What is tirzepatide for weight loss?

Tirzepatide is a once-weekly injection, given under the skin, that activates two hormone receptors, GIP and GLP-1. Among tirzepatide products, Zepbound injection, given under the skin, is FDA-approved for weight management in certain adults, while Mounjaro injection is approved only for uses in people with type 2 diabetes (checked October 14, 2026). About 15% to 21% average weight loss at 72 weeks vs about 3% on placebo (adults without diabetes). Results varied: about 1 in 11 to 1 in 7 did not lose at least 5%. Zepbound injection carries a boxed warning about thyroid C-cell tumors seen in rats.
Overview
Tirzepatide is a once-weekly injection, given under the skin, that activates two hormone receptors, GIP and GLP-1.[1] In a 72-week trial (SURMOUNT-1) of adults with obesity, or overweight with a weight-related condition, without diabetes, average weight loss was about 15% to 21% on tirzepatide, depending on the dose, compared with about 3% on placebo.[2] Results varied from person to person: in the same trial, about 1 in 11 to 1 in 7 people taking tirzepatide did not lose at least 5% of their body weight. The Zepbound label carries a boxed warning about thyroid C-cell tumors seen in rats. Evidence that tirzepatide lowers body weight in adults without diabetes comes from randomized controlled trials and from independent reviews of those trials.
How tirzepatide works
According to the Zepbound label, GLP-1 is a natural regulator of appetite and calorie intake, and nonclinical (laboratory and animal) studies suggest that GIP may add to that effect. The Zepbound label says tirzepatide lowers calorie intake, likely by affecting appetite, and slows stomach emptying, an effect that is largest after the first dose and lessens over time. The Zepbound label notes that, in animal studies, tirzepatide reached and activated nerve cells in brain areas involved in appetite and food intake. How tirzepatide acts in the body does not by itself show a health benefit; the evidence for weight loss comes from the clinical trials described on this page. The Zepbound label gives tirzepatide's half-life as about 5 to 6 days.
Evidence: how much weight people lose
In SURMOUNT-1, a 72-week trial of 2,539 adults with obesity, or overweight with a weight-related condition, without diabetes, average weight loss was 15.0% with tirzepatide 5 mg, 19.5% with 10 mg and 20.9% with 15 mg, compared with 3.1% with placebo. In SURMOUNT-1, everyone, including the placebo group, received lifestyle counseling aimed at eating about 500 fewer calories a day and at least 150 minutes of physical activity a week. According to the Zepbound label, 85.1%, 88.9% and 90.9% of people taking tirzepatide 5 mg, 10 mg and 15 mg in SURMOUNT-1 lost at least 5% of their body weight, compared with 34.5% on placebo. Results varied from person to person: in SURMOUNT-1, 14.9% of people on the 5 mg dose, 11.1% on 10 mg and 9.1% on 15 mg did not lose at least 5% of their body weight. According to the Zepbound label, 50.1% of people on tirzepatide 10 mg and 56.7% on 15 mg in SURMOUNT-1 lost at least 20% of their body weight, compared with 3.1% on placebo. The Zepbound label reports that 30.0% of people on tirzepatide 5 mg in SURMOUNT-1 lost at least 20% of their body weight, a result the label marks as not controlled for type I error. Compared with placebo, the Zepbound label reports extra average weight loss in SURMOUNT-1 of 11.9 percentage points with tirzepatide 5 mg, 16.4 with 10 mg and 17.8 with 15 mg. The SURMOUNT-1 weight results in the Zepbound label count every randomized participant, including the 14.3% to 16.4% of people on tirzepatide and 26.4% on placebo who stopped taking the study drug. Two independent reviews of trials in adults without diabetes, not funded by tirzepatide's maker, also found much greater weight loss with tirzepatide than with placebo.[3][4] An independent review of randomized trials in adults without diabetes, funded by the U.S. National Institutes of Health (Kommu 2025), found about 16 percentage points more weight loss with tirzepatide than with placebo (mean difference 16.32 points; 95% CI 14.29 to 18.35). Weight loss with tirzepatide is supported at the Established level only for adults without diabetes; the result in adults with type 2 diabetes comes from a single trial and is Emerging.
In a 72-week trial summarized in the Zepbound label (Study 2) of 938 adults with overweight or obesity and type 2 diabetes, average weight loss was 12.8% with tirzepatide 10 mg and 14.7% with 15 mg, compared with 3.2% with placebo. In adults with type 2 diabetes, average weight loss with tirzepatide in the Zepbound label's Study 2 was smaller than in SURMOUNT-1, which enrolled adults without diabetes. Results varied from person to person in Study 2: 20.8% of people on tirzepatide 10 mg and 17.2% on 15 mg did not lose at least 5% of their body weight.
In SURMOUNT-3, adults without diabetes who had first lost at least 5% of their weight in a 12-week intensive lifestyle program lost a further 18.4% of their body weight on average over 72 weeks with tirzepatide, while people on placebo gained 2.5%.[5] SURMOUNT-3 randomized only the people who lost at least 5% during the lifestyle program, and its authors noted that this may have produced a higher average weight loss; most participants were white and all were in the Americas. Results varied in SURMOUNT-3: 87.5% of people on tirzepatide lost a further 5% or more of their body weight, so about 1 in 8 did not.
Trial figures are group averages, and results varied from person to person in every trial. Every trial in this table was run in adults and lasted between 52 and 88 weeks, so the results do not show what happens over many years.
| Trial | Design | Who took part | Length | Main result | Funded by | Evidence level |
|---|---|---|---|---|---|---|
| SURMOUNT-1 [2] | Randomized, double-blind, placebo-controlled trial | 2,539 adults with obesity, or overweight with a weight-related condition, without diabetes | 72 weeks | Average weight loss 15.0% (5 mg), 19.5% (10 mg), 20.9% (15 mg) vs 3.1% on placebo | Eli Lilly (tirzepatide's maker) | Established (confirmed by two independent reviews) |
| Zepbound label Study 2 [1] | Randomized, double-blind, placebo-controlled trial | 938 adults with overweight or obesity and type 2 diabetes | 72 weeks | Average weight loss 12.8% (10 mg), 14.7% (15 mg) vs 3.2% on placebo | Not yet checked by us | Emerging (one trial, label summary) |
| SURMOUNT-3 [5] | Randomized, double-blind, placebo-controlled trial after a 12-week intensive lifestyle program | 579 adults without diabetes who first lost at least 5% with lifestyle changes | 12-week lifestyle program, then 72 weeks | Further average change −18.4% on tirzepatide vs +2.5% on placebo | Eli Lilly (tirzepatide's maker) | Emerging (one trial, lifestyle responders only) |
| SURMOUNT-4 [6] | Randomized withdrawal trial, double-blind | 670 adults without diabetes who had lost weight on tirzepatide (783 started) | 36 weeks on tirzepatide, then 52 weeks on tirzepatide or placebo | Weeks 36 to 88: −5.5% on tirzepatide vs +14.0% after switching to placebo (average) | Eli Lilly (tirzepatide's maker) | Emerging (funded by the maker) |
| SURMOUNT-OSA [7] | Two randomized, double-blind, placebo-controlled trials | 469 adults with moderate to severe obstructive sleep apnea and obesity, without diabetes | 52 weeks | About 20 and 24 fewer breathing interruptions per hour than placebo (AHI) | Eli Lilly (tirzepatide's maker) | Emerging (two trials, both funded by the maker) |
Sleep apnea
In two 52-week trials (SURMOUNT-OSA) of 469 adults with moderate to severe obstructive sleep apnea and obesity, without diabetes, tirzepatide reduced breathing interruptions during sleep by about 20 and 24 more events per hour than placebo. Breathing interruptions during sleep are measured as the apnea-hypopnea index (AHI); people in SURMOUNT-OSA started with an average of about 50 events per hour, and most had severe sleep apnea. In SURMOUNT-OSA, 42.2% and 50.2% of people on tirzepatide in the two trials ended with sleep apnea in remission or mild without symptoms, compared with 15.9% and 14.3% on placebo. Both SURMOUNT-OSA trials were funded by Eli Lilly, lasted 52 weeks and did not include people without obesity, and in the trial of people using a breathing machine (PAP), participants stopped PAP for 7 days before the main measurement. Tirzepatide's effect on sleep apnea is rated Emerging on this page because the randomized trial results we found in a PubMed search on October 1, 2026 come from the two SURMOUNT-OSA trials, both funded by the drug's maker. In a search of PubMed and Europe PMC on October 1, 2026, we found systematic reviews that cover tirzepatide in sleep apnea; the one we read in full (Altobaishat 2025), which reported no funding and no author conflicts of interest, pooled the two SURMOUNT-OSA trials with one trial of liraglutide, a different drug, added no other tirzepatide trial and rated the certainty of the pooled change in breathing interruptions as very low.[8]
What happens when people stop
In a trial funded by the drug's maker (SURMOUNT-4), adults without diabetes who had lost weight during 36 weeks on tirzepatide and were then switched to placebo saw their body weight rise by 14.0% on average over the next 52 weeks, while those who stayed on tirzepatide lost a further 5.5%.[6] In SURMOUNT-4, 89.5% of people who stayed on tirzepatide kept at least 80% of the weight they had lost in the first 36 weeks, compared with 16.6% of people switched to placebo. SURMOUNT-4 randomized only people who had tolerated tirzepatide for the first 36 weeks, so its results may not apply to everyone who starts the drug.
A second trial funded by the drug's maker (SURMOUNT-MAINTAIN) enrolled adults with obesity, or overweight with a weight-related condition, at 20 sites in the United States; after 60 weeks on tirzepatide 10 mg or 15 mg, 378 participants were randomly assigned to stay on that dose, step down to 5 mg or switch to placebo for another 52 weeks.[9] At week 112 of SURMOUNT-MAINTAIN, average weight loss from the start of the trial was 21.9% for people who stayed on their dose, 16.6% for people who stepped down to 5 mg and 9.9% for people switched to placebo.[9] From week 84 of SURMOUNT-MAINTAIN, people who had regained more than half of the weight they lost could restart tirzepatide as rescue treatment, and the trial's main analysis assumed that those people would not have gained further benefit from the treatment they had been assigned.
In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no reported results from a randomized trial in which people who stopped tirzepatide kept off as much weight, on average, as people who continued it.
Potential benefits
In SURMOUNT-1, waist size shrank by 14.0 cm, 17.7 cm and 18.5 cm on average with tirzepatide 5 mg, 10 mg and 15 mg, compared with 4.0 cm with placebo.
Evidence levels in this table follow our grading key: Established means consistent results from randomized trials or a systematic review of them; Emerging means some controlled human evidence that falls short of that, for example a single trial or trials funded mostly by the drug's maker; and a cell that begins "No reported results" means that our search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026 found none of that kind, which is different from saying that no such trial exists.
| Claimed benefit | Evidence level | Best source |
|---|---|---|
| Weight loss, adults without diabetes | Established (adults without diabetes) | SURMOUNT-1 trial; two independent reviews (Kommu 2025, Chen 2026) |
| Weight loss, adults with type 2 diabetes | Emerging (one trial, adults with type 2 diabetes) | Zepbound label, Study 2 |
| Keeping weight off on continued tirzepatide | Emerging (two trials, both funded by the maker) | SURMOUNT-4 and SURMOUNT-MAINTAIN (both funded by Eli Lilly) |
| Sleep apnea in adults with obesity | Emerging (two trials, both funded by the maker) | SURMOUNT-OSA (two trials, funded by Eli Lilly) |
| Waist size | Established (for the measurement, adults without diabetes) | SURMOUNT-1; independent review (Kommu 2025) |
| Blood pressure and blood fats | Emerging (measurements only; secondary results) | SURMOUNT-1 secondary results (Zepbound label) |
| Heart attack and stroke, adults without diabetes | No reported results from a randomized trial designed to test whether tirzepatide prevents heart attacks or strokes in people without diabetes; a registered trial, SURMOUNT-MMO, had posted no results (search of PubMed, Europe PMC and ClinicalTrials.gov, October 1, 2026) | Search of PubMed, Europe PMC and ClinicalTrials.gov, October 1, 2026 |
| Slowing aging or extending lifespan | No reported results from a trial designed to test aging or lifespan; four randomized trials and one non-randomized trial with a biological-age measure as a main outcome are registered, and none had posted results (search of PubMed, Europe PMC and ClinicalTrials.gov, October 1, 2026) | Search of PubMed, Europe PMC and ClinicalTrials.gov, October 1, 2026 |
In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no reported results from a human trial of tirzepatide with aging or biological age as its planned outcome; we found four registered randomized trials and one registered non-randomized trial that list a biological-age measure among their main outcomes, and none has reported results.[10][11][12][13][14] The four randomized trials (NCT07220473, NCT07293325, NCT07218445 and NCT07057310) plan to enroll 30 to 90 people each and to measure DNA methylation estimates of biological age after about 24 weeks; two of them also give a second weight-loss drug, and none lists lifespan or death as an outcome. The non-randomized trial (NCT07707778) plans to enroll 60 adults with HIV and obesity and to measure DNA methylation estimates of aging at 33 and 57 weeks, and it does not list lifespan or death as an outcome. In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no reported results from a trial designed to test whether tirzepatide extends lifespan; a registered trial, SURMOUNT-MMO, includes death from any cause in its main combined outcome and has not reported results.[15] SURPASS-CVOT, a trial funded by Eli Lilly, recorded deaths from any cause as a secondary outcome in adults with type 2 diabetes and cardiovascular disease, comparing tirzepatide with dulaglutide, another diabetes drug, with no placebo group; a result in that population and against that comparison is not evidence that tirzepatide extends life in people taking it for weight loss.[16][17] Weight loss, sleep apnea and blood-pressure results from tirzepatide trials are not evidence that tirzepatide slows aging or extends life.
Slowing aging or extending lifespan: Not an approved use of any tirzepatide product
Limitations
SURMOUNT-1, SURMOUNT-3, SURMOUNT-4, SURMOUNT-OSA and SURPASS-CVOT were all funded by Eli Lilly, the company that makes tirzepatide. The tirzepatide weight-loss trials whose results appear on this page measured body weight and related measurements such as waist size and blood pressure; they were not designed to show fewer heart attacks, strokes or deaths in people without diabetes. Most of what is known about tirzepatide for weight loss comes from trials in adults; the Zepbound label says its safety and effectiveness have not been established in children.
The Zepbound label says tirzepatide lowers body weight with greater fat mass loss than lean mass loss. Reviews of trials in adults with overweight or obesity, with or without type 2 diabetes, report that part of the weight lost with tirzepatide is lean mass rather than fat.[18][19] Lean mass loss with tirzepatide is rated Emerging on this page because the reviews we found did not state their funding sources in the records we read.
Risks
The Zepbound label's boxed warning says that in rats, tirzepatide causes thyroid C-cell tumors, and that it is unknown whether Zepbound causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, because the human relevance of the rat tumors has not been determined. The Zepbound label advises telling patients about possible signs of a thyroid tumor, such as a lump in the neck, trouble swallowing, shortness of breath or hoarseness that does not go away, and says routine blood calcitonin tests or thyroid ultrasounds are of uncertain value for finding MTC early.
The Zepbound label also warns about severe stomach and bowel reactions, kidney injury from dehydration, gallbladder problems, pancreatitis, serious allergic reactions, low blood sugar, worsening diabetic eye disease in people with type 2 diabetes, and inhaling stomach contents during anesthesia or deep sedation. According to the Zepbound prescribing information, "Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice." In the Zepbound label's pooled weight-loss trials, severe stomach and bowel reactions were reported by 1.7%, 2.5% and 3.1% of people on Zepbound 5 mg, 10 mg and 15 mg, compared with 1% on placebo, and the label says Zepbound is not recommended for people with severe gastroparesis. The Zepbound label reports acute kidney injury in 0.5% of people on Zepbound vs 0.2% on placebo in its pooled weight-loss trials, and says postmarketing reports, mostly in people who became dehydrated from stomach and bowel side effects, included some cases that needed dialysis. In the Zepbound label's pooled weight-loss trials, gallstones were reported by 1.1% of people on Zepbound vs 1% on placebo, and gallbladder inflammation by 0.7% vs 0.2%; the label says acute gallbladder events were associated with weight reduction. The Zepbound label warns that acute pancreatitis, including fatal cases, has been seen in people treated with GLP-1 receptor agonists or Zepbound; in its pooled weight-loss trials, confirmed pancreatitis was reported by 0.2% of people on Zepbound and 0.2% on placebo. The Zepbound label says Zepbound lowers blood sugar and can cause low blood sugar; in its trial of people with type 2 diabetes, blood sugar below 54 mg/dL was reported by 4.2% on Zepbound vs 1.3% on placebo, and more often in people also taking a sulfonylurea. In the Zepbound label's pooled weight-loss trials, serious allergic reactions were reported by 0.1% of people on Zepbound and by no one on placebo. The Zepbound label says people taking Zepbound should tell their healthcare providers before any planned surgery or procedure, because of rare reports of inhaling stomach contents during anesthesia or deep sedation in people taking GLP-1 receptor agonists. The Zepbound label says people with a history of diabetic eye disease (retinopathy) should be monitored, because temporary worsening has been reported with rapid improvement in blood sugar control.
Heart attack and stroke
In SURPASS-CVOT, a trial of 13,299 adults with type 2 diabetes and established cardiovascular disease, tirzepatide was about as effective as dulaglutide, another diabetes drug, at preventing heart attack, stroke or cardiovascular death counted together, and it was not shown to be better.[16] In SURPASS-CVOT, heart attack, stroke or cardiovascular death occurred in 12.2% of people on tirzepatide and 13.1% on dulaglutide (hazard ratio 0.92; 95.3% CI 0.83 to 1.01). SURPASS-CVOT enrolled only adults with type 2 diabetes and established cardiovascular disease, and it did not test people using tirzepatide for weight loss without diabetes. In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no reported results from a randomized trial designed to test whether tirzepatide prevents heart attacks or strokes in people without diabetes. SURMOUNT-MMO, a randomized trial of tirzepatide against placebo in adults without diabetes, is registered on ClinicalTrials.gov and had posted no results in the record we read on October 1, 2026; funded by Eli Lilly, it enrolled 15,374 adults aged 40 or older with a body-mass index of 27 or higher and cardiovascular disease or cardiovascular risk factors, and its main outcome counts deaths from any cause, heart attacks, strokes, coronary revascularization and heart-failure events together.[15] The Zepbound prescribing information (Revised 08/2026) contains no cardiovascular outcome results.
In SURMOUNT-1, systolic blood pressure fell by about 6 to 7 mmHg more with tirzepatide than with placebo, and triglycerides also fell more, but the Zepbound label marks these results as not controlled for type I error. The Zepbound label reports an average heart-rate increase of 1 to 3 beats per minute with Zepbound, compared with no increase on placebo. Blood pressure and blood fat levels are measurements, and changes in them do not show that tirzepatide prevents heart attacks or strokes.
Depression and suicidal thoughts
The Zepbound prescribing information (Revised 08/2026) lists "Suicidal Behavior and Ideation (Removed) 02/2026" under Recent Major Changes, and its current Warnings and Precautions section has no warning on suicidal behavior and ideation. In a post hoc analysis of three SURMOUNT trials in 4,056 adults without known major psychiatric illness, suicidal thoughts were reported by 0.6% of people in both the tirzepatide and placebo groups.[20] In the same post hoc analysis, depression questionnaire scores were not worse with tirzepatide than with placebo. Four of the analysis's authors were employees of Eli Lilly, tirzepatide's maker, and the authors wrote that further study in people with significant psychiatric illness may be warranted. These results do not show whether tirzepatide causes or prevents depression or suicidal thoughts, and anyone with new or worsening mood symptoms should talk to a licensed clinician.
Sources: Zepbound injection prescribing information, Revised 08/2026.
Side effects
According to the Zepbound prescribing information, "Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice." Nausea and diarrhea were the most common side effects in Table 1 of the Zepbound label: nausea was reported by 25% to 29% of people on Zepbound vs 8% on placebo, and diarrhea by 19% to 23% vs 8%. In the Zepbound label's pooled weight-loss trials, stomach and bowel side effects were reported by 56% of people at each Zepbound dose, compared with 30% on placebo, and most nausea, vomiting and diarrhea happened while the dose was being increased and decreased over time. An independent review of six tirzepatide trials in adults without diabetes (Kommu 2025) found nausea, diarrhea and constipation reported about 3 times as often, and vomiting about 6 times as often, with tirzepatide as with placebo. In the SURMOUNT trials, most stomach and bowel side effects were mild to moderate, according to the trial reports. In the Zepbound label's pooled weight-loss trials, 4.8%, 6.3% and 6.7% of people on Zepbound 5 mg, 10 mg and 15 mg stopped treatment because of side effects, compared with 3.4% on placebo, most often during the first few months and because of stomach and bowel side effects.
According to the Zepbound prescribing information, "Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice." Table 1 of the Zepbound prescribing information (Revised 08/2026), all 16 rows: "Adverse Reactions (≥2% and Greater than Placebo) in ZEPBOUND-Treated Adults with Obesity or Overweight in Weight Reduction and Long-term Maintenance Trials (Study 1 and Study 2)." Numbers of people in Table 1: placebo 958; Zepbound 5 mg 630; Zepbound 10 mg 948; Zepbound 15 mg 941. The Zepbound label's Table 1 pools two trials of up to 72 weeks, one of which enrolled only people with type 2 diabetes; 25% of the pooled patients had type 2 diabetes.
| Side effect | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| Nausea | 8% | 25% | 29% | 28% |
| Diarrhea | 8% | 19% | 21% | 23% |
| Vomiting | 2% | 8% | 11% | 13% |
| Constipation | 5% | 17% | 14% | 11% |
| Abdominal pain | 5% | 9% | 9% | 10% |
| Dyspepsia (indigestion) | 4% | 9% | 9% | 10% |
| Injection site reactions | 2% | 6% | 8% | 8% |
| Fatigue | 3% | 5% | 6% | 7% |
| Hypersensitivity reactions | 3% | 5% | 5% | 5% |
| Eructation (belching) | 1% | 4% | 5% | 5% |
| Hair loss | 1% | 5% | 4% | 5% |
| Gastroesophageal reflux disease (GERD) | 2% | 4% | 4% | 5% |
| Flatulence (gas) | 2% | 3% | 3% | 4% |
| Abdominal distension (bloating) | 2% | 3% | 3% | 4% |
| Dizziness | 2% | 4% | 5% | 4% |
| Hypotension (low blood pressure) | 0% | 1% | 1% | 2% |
In Table 1, diarrhea includes diarrhea and frequent bowel movements. In Table 1, constipation includes constipation and hard stools. In Table 1, abdominal pain includes abdominal discomfort, abdominal pain, lower and upper abdominal pain, and abdominal tenderness. In Table 1, injection site reactions include several related terms, such as bruising, redness, itching, pain and rash at the injection site. In Table 1, fatigue includes weakness, fatigue, lack of energy and generally feeling unwell. In Table 1, hypotension includes decreased blood pressure, hypotension and orthostatic hypotension (a drop in blood pressure on standing).
Sources: Zepbound injection prescribing information, Revised 08/2026.
If you have severe symptoms, call 911 or seek emergency care. Report side effects to FDA MedWatch.
Contraindication considerations
The Zepbound label says people should not use Zepbound if they or a family member have had medullary thyroid carcinoma (MTC), if they have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), or if they have had a serious allergic reaction to tirzepatide or any ingredient in Zepbound.
The Zepbound label says Zepbound may make birth-control pills less effective because it slows stomach emptying, an effect that is largest after the first dose and lessens over time. The Zepbound label advises people using birth-control pills to switch to a non-oral method, or to add a barrier method, for 4 weeks after starting Zepbound and for 4 weeks after each dose increase. The Zepbound label says hormonal birth control that is not taken by mouth should not be affected. After a single 5 mg dose, the Zepbound label reports that peak blood levels of the hormones in a combined birth-control pill fell by 55% to 66%.
The Zepbound label says weight loss offers no benefit during pregnancy and may harm the fetus, and advises stopping Zepbound when a pregnancy is recognized. The Zepbound label does not give a time to stop Zepbound before a planned pregnancy. In animal studies described in the Zepbound label, tirzepatide reduced fetal growth and caused fetal abnormalities in rats, effects that happened alongside reduced weight and food intake in the mothers.
In a study of 11 breastfeeding women after one 5 mg dose, the Zepbound label reports that tirzepatide could not be detected in 164 of 171 breast-milk samples; there are no data on effects in breastfed infants.
Sources: Zepbound injection prescribing information, Revised 08/2026.
Administration methods
The Zepbound label starts at 2.5 mg injected under the skin once weekly for 4 weeks, and says the 2.5 mg dose is for starting treatment, not for maintenance. After the starting dose, the Zepbound label moves to 5 mg once weekly, and says the dose may be raised in 2.5 mg steps after at least 4 weeks on the current dose. The Zepbound label says the dose is raised gradually to reduce the risk of stomach and bowel side effects. The Zepbound label lists maintenance doses of 5 mg, 10 mg or 15 mg once weekly for weight reduction and 10 mg or 15 mg once weekly for sleep apnea, with 15 mg once weekly as the highest dose for any use. The Zepbound label says: "administer ZEPBOUND as soon as possible within 4 days (96 hours) after the missed dose. If more than 4 days have passed, skip the missed dose and administer the next dose on the regularly scheduled day." The Zepbound label allows the weekly injection day to be changed as long as the two doses are at least 3 days (72 hours) apart. The Zepbound label says Zepbound can be injected once weekly at any time of day, with or without meals, in the abdomen or thigh, or in the back of the upper arm by another person, rotating the injection site with each dose. The Zepbound label says patients or caregivers should be trained before the first injection, and that the Zepbound KwikPen is not recommended for self-injection by people who are visually impaired. The Zepbound label lists four forms: a single-dose pen, a single-dose vial, a multi-dose vial and a single-patient-use KwikPen, and says a KwikPen must never be shared between people, even if the needle is changed. A licensed prescriber decides the starting dose, when to raise it and the maintenance dose for each person.
Dose schedules on this page summarize the Zepbound injection prescribing information and are not instructions to follow. A prescriber sets and adjusts the dose.
Dose steps as written in the Zepbound prescribing information, Section 2 (Revised 08/2026); a prescriber sets the actual dose.
| Step | Zepbound label |
|---|---|
| Starting dose | 2.5 mg once weekly for 4 weeks (for starting, not maintenance) |
| Next step | 5 mg once weekly |
| Dose steps | Up by 2.5 mg, after at least 4 weeks on the current dose |
| Weight maintenance | 5 mg, 10 mg or 15 mg once weekly |
| Sleep apnea maintenance | 10 mg or 15 mg once weekly |
| Highest dose | 15 mg once weekly |
Sources: prescribing information, Section 2 (Dosage and Administration), for Zepbound injection prescribing information, Revised 08/2026.
Insurance
Coverage varies by plan and can depend on the reason it is prescribed. Confirm coverage, and any prior authorization, with your insurer.
FDA and regulatory status
Among tirzepatide products, Zepbound injection, given under the skin, is FDA-approved for weight management in certain adults, while Mounjaro injection is approved only for uses in people with type 2 diabetes (checked October 14, 2026).
The FDA status table lists each tirzepatide product with its route and the uses in its prescribing information.
| Product | How it is given | What it's FDA-approved for | Label |
|---|---|---|---|
| Zepbound injection | given as an injection under the skin | Zepbound (tirzepatide) injection, given under the skin, is FDA-approved, with a reduced-calorie diet and more physical activity, to reduce excess body weight and keep it off long term in adults with obesity, or in adults with overweight who have at least one weight-related condition. It is also approved to treat moderate to severe obstructive sleep apnea in adults with obesity. It requires a prescription. Source: FDA prescribing information. | Zepbound injection prescribing information, Revised 08/2026 |
| Mounjaro injection | given as an injection under the skin | Mounjaro (tirzepatide) injection, given under the skin, is FDA-approved, along with diet and exercise, to improve blood sugar control in adults and children 10 years and older with type 2 diabetes. It is also approved to lower the risk of major cardiovascular events in adults with type 2 diabetes who are at high risk for these events. It requires a prescription. Source: FDA prescribing information. | Mounjaro injection prescribing information, Revised 08/2026 |
Mounjaro injection is not FDA-approved for weight management. Its approved uses are listed in the FDA status table. Prescribing it for weight management is off-label. For weight management in certain adults, together with a reduced-calorie diet and more physical activity, FDA has approved Zepbound injection, given under the skin.
Tirzepatide is not FDA-approved for anti-aging, longevity or general wellness. FDA has approved specific tirzepatide products only for specific uses: Mounjaro injection for uses in people with type 2 diabetes, and Zepbound injection for weight management and for obstructive sleep apnea in certain adults. Using tirzepatide for anti-aging or longevity is off-label. FDA has not reviewed whether it is safe and effective for that purpose.
Each tirzepatide product in the FDA status table is available only with a prescription (checked October 14, 2026).
Completing an intake form or making a payment does not guarantee a prescription.
Compounded tirzepatide
Compounded tirzepatide is a different product from Zepbound injection.
Compounded tirzepatide is not FDA-approved. FDA states: 'Compounded drugs are not FDA-approved. This means that FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed.' FDA determined that the tirzepatide injection shortage was resolved on December 19, 2024, and said on April 1, 2026 that tirzepatide was not on its drug shortage list.
In a Federal Register notice published May 1, 2026, FDA proposed not to include tirzepatide on the list of bulk drug substances that outsourcing facilities may use in compounding (the 503B Bulks List). As of October 14, 2026, we have not found a final decision.
In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no randomized trial of a compounded tirzepatide product. The trial results on this page come from studies of tirzepatide made by Eli Lilly and cannot be assumed to apply to compounded versions.
Regulatory status checked October 14, 2026. Sources: www.accessdata.fda.gov/…/215866s044s045lbl.pdf; www.accessdata.fda.gov/…/215866Orig1s044,215866Orig1s045ltr.pdf; www.accessdata.fda.gov/…/217806Orig1s041correctedlbl.pdf; www.fda.gov/…/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize; public-inspection.federalregister.gov/…/2026-08552.pdf; www.fda.gov/…/compounding-and-fda-questions-and-answers; www.fda.gov/…/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
Prescription requirements
Each tirzepatide product in the FDA status table is available only with a prescription (checked October 14, 2026).
Completing an intake form or making a payment does not guarantee a prescription.
FAQs
How does tirzepatide work for weight loss?
According to the Zepbound label, GLP-1 is a natural regulator of appetite and calorie intake, and nonclinical (laboratory and animal) studies suggest that GIP may add to that effect. The Zepbound label says tirzepatide lowers calorie intake, likely by affecting appetite, and slows stomach emptying, an effect that is largest after the first dose and lessens over time.
What happens when you stop taking tirzepatide?
In a trial funded by the drug's maker (SURMOUNT-4), adults without diabetes who had lost weight during 36 weeks on tirzepatide and were then switched to placebo saw their body weight rise by 14.0% on average over the next 52 weeks, while those who stayed on tirzepatide lost a further 5.5%. In SURMOUNT-4, 89.5% of people who stayed on tirzepatide kept at least 80% of the weight they had lost in the first 36 weeks, compared with 16.6% of people switched to placebo. SURMOUNT-4 randomized only people who had tolerated tirzepatide for the first 36 weeks, so its results may not apply to everyone who starts the drug. Zepbound injection carries a boxed warning about thyroid C-cell tumors seen in rats. In a search of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no reported results from a randomized trial in which people who stopped tirzepatide kept off as much weight, on average, as people who continued it.
Does tirzepatide affect birth control pills?
The Zepbound label says Zepbound may make birth-control pills less effective because it slows stomach emptying, an effect that is largest after the first dose and lessens over time. The Zepbound label advises people using birth-control pills to switch to a non-oral method, or to add a barrier method, for 4 weeks after starting Zepbound and for 4 weeks after each dose increase. The Zepbound label says hormonal birth control that is not taken by mouth should not be affected.
Provider directory
Both links below open the Medical weight management category of the provider directory.
Compounded tirzepatide is not FDA-approved. See FDA's statement.
You can connect with a licensed provider to ask about an evaluation.
Find a Provider · Connect With a Licensed Provider
A licensed clinician decides whether treatment is appropriate. A prescription is not guaranteed.
Related diagnostics and treatments
References
- Eli Lilly and Company. ZEPBOUND (tirzepatide) injection, for subcutaneous use. Prescribing Information, Revised 08/2026. U.S. Food and Drug Administration, Drugs@FDA. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806Orig1s041correctedlbl.pdf (DailyMed setid 487cd7e7-434c-4925-99fa-aa80b1cc776b, SPL version 40). Accessed 2026-09-28.
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038. PMID 35658024. Accessed 2026-09-28.
- Kommu S, Sharma PP, Gabor RM. Efficacy and Safety of Tirzepatide on Weight Loss in Patients Without Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Obes Rev. 2025;26(11):e13961. doi:10.1111/obr.13961. PMID 40510020; PMCID PMC12531717. Accessed 2026-09-28.
- Chen D, Ma B, Sun H, et al. Comparative efficacy and safety of glucagon-like peptide 1 based drugs for weight loss in adults with overweight or obesity without diabetes: network meta-analysis of randomised controlled trials. BMJ Med. 2026;5(1):e003026. doi:10.1136/bmjmed-2026-003026. PMID 42688617; PMCID PMC13536023. Accessed 2026-09-28.
- Wadden TA, Chao AM, Machineni S, et al. Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity: the SURMOUNT-3 phase 3 trial. Nat Med. 2023;29(11):2909-2918. doi:10.1038/s41591-023-02597-w. PMID 37840095; PMCID PMC10667099. Accessed 2026-09-28.
- Aronne LJ, Sattar N, Horn DB, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. 2024;331(1):38-48. doi:10.1001/jama.2023.24945. PMID 38078870; PMCID PMC10714284. Accessed 2026-09-28.
- Malhotra A, Grunstein RR, Fietze I, et al. Tirzepatide for the Treatment of Obstructive Sleep Apnea and Obesity. N Engl J Med. 2024;391(13):1193-1205. doi:10.1056/NEJMoa2404881. PMID 38912654; PMCID PMC11598664. An erratum to this article exists (PMID 39413392). Accessed 2026-09-28.
- Altobaishat O, Farid Gadelmawla A, Balbaa E, Turkmani M, Abouzid M. Safety and efficacy of glucagon-like peptide-1 receptor agonists in patients with obstructive sleep apnea: a systematic review and meta-analysis of randomized controlled trials. Eur Clin Respir J. 2025;12(1):2484048. doi:10.1080/20018525.2025.2484048. PMID 40144943; PMCID PMC11938315. Accessed 2026-10-01.
- Horn DB, Aronne LJ, Wharton S, et al. Tirzepatide for maintenance of bodyweight reduction in people with obesity in the USA (SURMOUNT-MAINTAIN): a multicentre, double-blind, randomised, placebo-controlled trial. Lancet. 2026;407(10545):2305-2318. doi:10.1016/S0140-6736(26)00656-2. PMID 42119587. An erratum to this article exists (PMID 42242249). Accessed 2026-10-01.
- ClinicalTrials.gov. Tirzepatide to Slow Biological Aging. Identifier NCT07220473. Last update posted 2026-03-24. https://clinicaltrials.gov/study/NCT07220473. Accessed 2026-10-01.
- ClinicalTrials.gov. Semaglutide and Tirzepatide for Genetic Aging Delay in Adults With Obesity. Identifier NCT07293325. Last update posted 2025-12-19. https://clinicaltrials.gov/study/NCT07293325. Accessed 2026-10-01.
- ClinicalTrials.gov. The Effect of Tirzepatide on Menopausal Vasomotor Symptoms and Biological Aging in Post-menopausal Women With Obesity. Identifier NCT07218445. Last update posted 2026-08-18. https://clinicaltrials.gov/study/NCT07218445. Accessed 2026-10-01.
- ClinicalTrials.gov. Aging Well: Targeting Obesity With GLP-1 Agonists to Enhance Physical and Vascular Health in Postmenopausal Women. Identifier NCT07057310. Last update posted 2026-07-20. https://clinicaltrials.gov/study/NCT07057310. Accessed 2026-10-01.
- ClinicalTrials.gov. Tirzepatide's Effects on Epigenetic Aging and Metabolic Restoration in Virally Suppressed People With HIV. Identifier NCT07707778. Last update posted 2026-07-20. https://clinicaltrials.gov/study/NCT07707778. Accessed 2026-10-01.
- ClinicalTrials.gov. A Study of Tirzepatide (LY3298176) on the Reduction on Morbidity and Mortality in Adults With Obesity (SURMOUNT-MMO). Identifier NCT05556512. Last update posted 2026-09-22. https://clinicaltrials.gov/study/NCT05556512. Accessed 2026-10-01.
- Nicholls SJ, Pavo I, Bhatt DL, et al. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes. N Engl J Med. 2025;393(24):2409-2420. doi:10.1056/NEJMoa2505928. PMID 41406444. Accessed 2026-09-28.
- ClinicalTrials.gov. A Study of Tirzepatide (LY3298176) Compared With Dulaglutide on Major Cardiovascular Events in Participants With Type 2 Diabetes (SURPASS-CVOT). Identifier NCT04255433. Last update posted 2026-07-08. https://clinicaltrials.gov/study/NCT04255433. Accessed 2026-10-01.
- Eisa N, et al. Lean Mass Changes With Incretin Therapy Versus Lifestyle Intervention: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Diabetes Obes Metab. 2026;28(6):4818-4827. doi:10.1111/dom.70666. PMID 41877354. Accessed 2026-09-27.
- Karakasis P, et al. Effect of glucagon-like peptide-1 receptor agonists and co-agonists on body composition: Systematic review and network meta-analysis. Metabolism. 2025;164:156113. doi:10.1016/j.metabol.2024.156113. PMID 39719170. Accessed 2026-09-27.
- Wadden TA, Oquendo MA, Kushner RF, et al. Psychiatric Safety of Tirzepatide in People With Obesity and No Known Major Psychopathology: A Post Hoc Analysis of SURMOUNT. Obesity (Silver Spring). 2026;34(3):565-578. doi:10.1002/oby.70122. PMID 41537305. Accessed 2026-09-28.