What is an iron infusion, and what does the evidence show?

Several different IV iron products exist, each with its own ingredients, label and warnings.

How iron deficiency is confirmed

The British Society of Gastroenterology's 2021 guideline for adults recommends confirming iron deficiency with blood tests called iron studies before investigating its cause.[1] Serum ferritin is "the single most useful marker" of iron deficiency anemia, the British Society of Gastroenterology guideline says, and other blood tests, such as transferrin saturation, can help when a normal ferritin result may be misleading.[1]

A serum ferritin level below 15 micrograms per liter indicates absent iron stores and a level below 30 generally indicates low iron stores, according to the British Society of Gastroenterology guideline.[1] A 2023 European Society of Cardiology guideline update on heart failure states that iron deficiency was diagnosed by a transferrin saturation below 20% or a serum ferritin below 100 micrograms per liter, citing two of the IV iron trials.[2] Ferritin cut-offs for iron deficiency differ between guidelines and between health conditions, so one number does not apply to everyone.

The INFeD prescribing information carries a boxed warning about anaphylactic-type reactions, including fatal reactions, some after a test dose was tolerated. It says to give a test dose before the first full dose, to have resuscitation equipment and trained personnel readily available, and to 'Use INFeD only in patients in whom clinical and laboratory investigations have established an iron deficient state not amenable to oral iron therapy.'

Sources: INFeD injection prescribing information, Revised 08/2024.

Evidence for IV iron by group

IV iron evidence by group: established for some results in pregnancy, after childbirth and in heart failure with iron deficiency; mixed for tiredness with low iron stores and no anemia; against a benefit for blood transfusion before major abdominal surgery; none found for energy or tiredness in general-population adults without iron deficiency (PubMed, Europe PMC, ClinicalTrials.gov, October 1, 2026).

Evidence levels in this table follow our grading key: Established means consistent results from randomized trials or a systematic review of them, or that a guideline or expert body says something; Emerging means some controlled human evidence that falls short of that, such as small or short trials, mixed results or trials funded by a maker; Evidence against means controlled trials tested the claim on its main result and did not find it; and "no support found" means the searches named in that cell found none. In this table, None found means our searches of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026 found no published study for that cell.

IV iron compared with iron tablets

The British Society of Gastroenterology's 2021 guideline recommends one iron tablet a day as the first treatment for iron deficiency anemia in adults, and says injected or infused iron should be considered when tablets should not be used, do not work or are not tolerated.[1] The two head-to-head comparisons of IV iron and iron tablets that we graded as established both come from Cochrane reviews, one in pregnancy and one after childbirth. In searches of PubMed and Europe PMC on October 1, 2026, most of the systematic reviews we found that compare IV iron with iron tablets cover one patient group, such as pregnancy, kidney disease or surgery. Some cover more than one group, and we read two of them.[3][4] A 2014 Cochrane review of 21 trials with 4,745 anemic adults who were not pregnant or breastfeeding and did not have chronic kidney disease found that hemoglobin rose modestly more with injected or infused iron than with iron tablets (6 trials, 769 people, very low-quality evidence), a blood test result that its authors described as without clinical benefit.[3] A 2026 systematic review of 31 studies compared IV iron with iron tablets across several conditions and reported larger hemoglobin rises with IV iron in chronic kidney disease, inflammatory bowel disease, cancer-related anemia and iron deficiency anemia in general, and no significant difference for anemia after surgery or restless legs syndrome; its authors noted substantial heterogeneity, and its summary gives no certainty rating.[4] Each comparison of IV iron and iron tablets applies to the group that was studied and does not show which treatment suits any one person.

Heart failure with iron deficiency

A 2025 meta-analysis pooled results for 6,339 people with heart failure and iron deficiency from 10 trials and found lower odds of a first heart failure hospitalization or cardiovascular death with IV iron than with placebo or usual care (odds ratio 0.73, 95% confidence interval 0.58 to 0.92).[5] Its authors reported no financial support for the study, and the Qatar National Library funded the article's publication.[5] That meta-analysis was first published in July 2024, before FAIR-HF2 reported in 2025, so its pooled result does not include FAIR-HF2.[5][6] The main result of each large trial fell short of statistical significance on the trial's own terms: AFFIRM-AHF (1,108 people analysed, p = 0.059), IRONMAN (1,137 people, p = 0.070), HEART-FID (3,065 people), which set a stricter threshold of 0.01 and reported no apparent difference between ferric carboxymaltose and placebo on its main combined measure, and FAIR-HF2 (1,105 people), whose three main results (p = 0.04, 0.12 and 0.07) did not meet the thresholds the trial had set in advance.[6][7][8][9] AFFIRM-AHF was funded by Vifor Pharma, HEART-FID by American Regent, and IRONMAN by the British Heart Foundation and Pharmacosmos. FAIR-HF2 was financed by the German Center for Cardiovascular Research, the German Heart Foundation and CSL Vifor, which gave an unrestricted grant and supplied the trial's ferric carboxymaltose free of charge. Vifor Pharma, American Regent and Pharmacosmos make IV iron products.[6][7][8][9] With data from 12 of its 14 trials, a 2025 meta-analysis of IV iron in heart failure with iron deficiency found no significant difference in death from any cause between IV iron and the comparison groups (odds ratio 0.95, 95% confidence interval 0.84 to 1.07).[5]

A 2023 European Society of Cardiology guideline update recommends IV iron for people who have symptoms of heart failure with a reduced or mildly reduced ejection fraction and iron deficiency, to ease heart failure symptoms and improve quality of life (Class I, Level A, the guideline's highest class of recommendation and level of evidence).[2] The 2023 European Society of Cardiology guideline update says IV iron with ferric carboxymaltose or ferric derisomaltose "should be considered" in the same patients to reduce the risk of heart failure hospitalization (Class IIa, Level A).[2]

The heart failure findings apply to people with heart failure and confirmed iron deficiency, not to people with heart failure in general or to healthy adults.

Injectafer (ferric carboxymaltose) injection, given into a vein, is FDA-approved for the treatment of iron deficiency anemia in adults and children 1 year and older who have intolerance or an unsatisfactory response to oral iron, and in adults with non-dialysis dependent chronic kidney disease. It is also FDA-approved for iron deficiency in adults with heart failure (New York Heart Association class II/III) to improve exercise capacity. It requires a prescription. Source: FDA prescribing information.

The FDA status table on this page lists the uses in each product's prescribing information.

Pregnancy and after childbirth

In pregnant women with iron deficiency anemia, a 2024 Cochrane review found that IV iron likely raises hemoglobin slightly more than iron tablets around birth (6 trials, 1,574 women, moderate certainty) and likely leaves fewer women anemic around birth (4 trials, 1,240 women, moderate certainty).[10] The Cochrane pregnancy review covered 13 trials with 3,939 women whose hemoglobin was below 11 grams per deciliter, and 8 of the 13 trials were run in India or Africa.[10]

Reviews disagree on blood transfusion in pregnancy: the 2024 Cochrane review found IV iron likely makes little to no difference to the need for a transfusion compared with iron tablets (6 trials, 2,592 women, moderate certainty), while a 2026 meta-analysis reported a lower transfusion rate during the delivery hospital stay with IV iron (14 studies, with no certainty rating in its summary).[10][11] The 2024 Cochrane review found IV iron may make little to no difference to heavy bleeding after birth compared with iron tablets (3 trials, 2,251 women, low certainty).[10]

On safety in pregnancy, the 2024 Cochrane review found IV iron may not increase serious side effects compared with iron tablets (1 trial, 1,934 women, low certainty), and its authors noted that the result could not rule out harm.[10] The Injectafer and Monoferric labels say that severe reactions to IV iron in pregnancy, such as a severe drop in blood pressure or shock, may cause a slow heart rate in the unborn baby, especially in the second and third trimesters.[12][13]

Sources: Injectafer injection prescribing information, Revised 08/2026; Monoferric injection prescribing information, Revised 08/2022.

After childbirth, a 2024 Cochrane review found IV iron probably reduces tiredness slightly in the first 8 to 28 days compared with iron tablets (2 trials, 515 women, moderate certainty) and probably makes little to no difference after four weeks.[14] Iron tablets probably cause much more constipation than IV iron after childbirth, according to the 2024 Cochrane review of treatment after childbirth (10 trials, 1,798 women, moderate certainty).[14] One author of the Cochrane review of treatment after childbirth had run two trials funded by Pharmacosmos, an IV iron maker, and both trials were included in the review.[14] For death and for serious allergic reactions after childbirth, the 2024 Cochrane review could not tell whether IV iron differs from iron tablets (for allergic reactions: 12 trials, 2,195 women, very low certainty).[14] The authors of the Cochrane review of treatment after childbirth describe hemoglobin as a surrogate outcome and say treatment decisions should rest on outcomes that matter to patients.[14]

Before surgery

In a double-blind trial of 487 adults with anemia before major open abdominal surgery, IV iron given 10 to 42 days beforehand did not lower the combined rate of death or blood transfusion compared with placebo (29% with IV iron, 28% with placebo).[15] A 2019 Cochrane review of iron treatment before surgery, given by mouth or into a vein, found no difference in the share of people who received a blood transfusion compared with placebo or usual care (4 trials, 200 people, moderate-quality evidence).[16] Compared with iron tablets, IV iron raised hemoglobin more before surgery in the 2019 Cochrane review of iron before surgery (2 trials, 172 people, low-quality evidence); that is a blood test result, and the review's authors wrote that these results do not provide reliable evidence.[16] The 2019 Cochrane review of iron before surgery reports that its lead author had received fees from two IV iron makers, Pharmacosmos and Vifor, and that an author without such ties re-checked the data.[16]

Low iron stores without anemia

A 2019 Cochrane review of 11 studies with 1,074 adults who had iron deficiency without anemia concluded that the evidence was insufficient to show a benefit of IV iron beyond a small rise in hemoglobin, which the authors called clinically insignificant.[17] The 2019 Cochrane review also pooled a fatigue scale from 3 studies, rated that evidence very low quality, and said its authors remained uncertain about the role of IV iron for that measure.[17] In adults with iron deficiency and no anemia, IV iron may raise hemoglobin by 3.04 grams per liter on average compared with placebo, according to the 2019 Cochrane review (8 studies, 548 people, low-quality evidence); its authors described the rise as of limited clinical significance.[17]

In a placebo-controlled trial of 405 repeat blood donors without anemia whose ferritin was 50 micrograms per liter or lower, fatigue scores 6 to 8 weeks after a single 800 mg dose of ferric carboxymaltose were 3.9 with IV iron and 4.0 with placebo (p = 0.819), while ferritin and hemoglobin rose more with IV iron.[18] The blood donor trial was funded by the Humanitarian Foundation of the Swiss Red Cross, and Vifor supplied the iron product.[18]

In a trial of 90 premenopausal women with fatigue, no anemia and ferritin of 50 nanograms per milliliter or lower, fatigue fell by 1.1 points with 800 mg of IV iron sucrose and by 0.7 points with placebo over 6 weeks, a difference that was not statistically significant (p = 0.07); among the women whose ferritin was 15 or lower, the fall was 1.8 points with IV iron and 0.4 with placebo (p = 0.005).[19] In a single-blinded trial of 290 women with fatigue and iron deficiency, fatigue improved by at least 1 point in 65.3% of those given 1,000 mg of ferric carboxymaltose and in 52.7% of those given saline; one author was an employee of Vifor Pharma, an IV iron maker, and Vifor Pharma paid for medical writing.[20]

The FDA status table on this page lists the uses in each product's prescribing information.

In searches of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no trial of IV iron for energy, fatigue or wellbeing in adults from the general population who are not iron-deficient. A registered ClinicalTrials.gov trial of iron sucrose compared with placebo in women aged 18 to 45, completed in March 2024 with a fatigue score as its main measure, had posted no results as of October 1, 2026. Its title describes non-anemic iron-deficient women, while its eligibility text reads 'reproductive age non-anemic fatigued' and lists no ferritin cut-off.[21] One small trial enrolled 14 distance runners described as having no clinical iron deficiency, with ferritin of 30 to 100 micrograms per liter; after three 100 mg injections of ferric carboxymaltose over four weeks, fatigue and mood scores at week 6 were better than with saline, with no significant change in hemoglobin mass and no significant improvement in 3,000 meter run times. We grade this as emerging evidence, because it is one small trial in trained runners.[22] In a placebo-controlled trial of 48 people with chronic obstructive pulmonary disease whose average ferritin was 97.1 micrograms per liter, one dose of ferric carboxymaltose did not change blood oxygen levels, the trial's main measure, after one week; walking distance and a breathlessness score were better in secondary analyses that the authors said need confirmation, and low blood phosphate was more frequent with the iron (91.7% compared with 8.3% with placebo).[23] The Feraheme and Monoferric labels warn that too much iron given by vein can lead to excess iron stored in the body, and both say not to give the product to people with iron overload.[13][24]

Sources: Feraheme injection prescribing information, Revised 05/2026; Monoferric injection prescribing information, Revised 08/2022.

The IV iron products whose labels we reviewed are FDA-approved for iron deficiency or iron deficiency anemia in certain patients; none of those labels covers use in people who are not iron-deficient (checked September 30, 2026).

None of the IV iron product labels we reviewed lists aging or longevity as an approved use; those products are approved for iron deficiency or iron deficiency anemia in certain patients (checked September 30, 2026).

Limitations of the evidence

Most of the trials described on this page studied people with a diagnosed condition, such as heart failure, anemia in pregnancy or anemia before surgery, and none studied general-population adults seeking an infusion for energy. Hemoglobin and ferritin are blood test results, and a rise in either does not by itself show that a person feels or functions better.[14][18]

Several of the trials we reviewed were funded wholly or in part by companies that make or supply IV iron products, including the four large heart failure trials described on this page.[6][7][8][9][25][26][27][28][29]

Is an iron infusion FDA-approved?

FDA has approved specific IV iron products for iron deficiency or iron deficiency anemia in certain patients, including people who could not tolerate or did not respond to oral iron (checked September 30, 2026).

The FDA status table lists each IV iron product whose label we reviewed, with how it is given, the uses in its prescribing information, and a link to the label. The warnings in these labels are in the section on risks.

Each IV iron product in the FDA status table is available only with a prescription (checked September 30, 2026).

Completing an intake form or making a payment does not guarantee a prescription.

Whether a product is appropriate for a specific person is decided by a licensed clinician using that product's prescribing information.

Regulatory status checked September 30, 2026. Sources: www.accessdata.fda.gov/…/017441s181lbl.pdf; www.accessdata.fda.gov/…/022180s026lbl.pdf; www.accessdata.fda.gov/…/203565s030lbl.pdf; www.accessdata.fda.gov/…/208171s003lbl.pdf; www.accessdata.fda.gov/…/021135Orig1s042lbl.pdf; www.accessdata.fda.gov/…/020955s020lbl.pdf; www.accessdata.fda.gov/…/203565Orig1s030ltr.pdf

What are the side effects of an iron infusion?

The labels of all six IV iron products we reviewed warn about serious allergic reactions.[12][13][24][30][31][32] The most common side effects listed on the Injectafer label for adults are nausea, high blood pressure, flushing, injection site reactions, skin redness, low blood phosphate and dizziness; the Monoferric label lists rash and nausea.[12][13]

Allergy warnings in each label

The INFeD prescribing information carries a boxed warning about anaphylactic-type reactions, including fatal reactions, some after a test dose was tolerated. It says to give a test dose before the first full dose, to have resuscitation equipment and trained personnel readily available, and to 'Use INFeD only in patients in whom clinical and laboratory investigations have established an iron deficient state not amenable to oral iron therapy.'

The Feraheme prescribing information carries a boxed warning that fatal and serious hypersensitivity reactions, including anaphylaxis, have occurred, also in patients who had tolerated an earlier dose. It says to give Feraheme only as an intravenous infusion over at least 15 minutes, only when personnel and therapies are immediately available to treat these reactions, and to watch patients for at least 30 minutes afterwards, with blood pressure and pulse checks.

The Monoferric, Venofer and Ferrlecit prescribing information we reviewed has no boxed warning. Each label warns that serious hypersensitivity reactions, including anaphylactic-type reactions, some of which have been life-threatening and fatal, have been reported.

Allergic reactions in studies

In a study of Medicare records for older adults who received a first dose of IV iron between July 2013 and December 2018, the adjusted rate of anaphylaxis per 10,000 first doses was 9.8 for iron dextran, 4.0 for ferumoxytol, 1.5 for ferric gluconate, 1.2 for iron sucrose and 0.8 for ferric carboxymaltose.[33] The authors of the Medicare study concluded: "The rates of anaphylaxis were very low with all IV iron products but were 3- to 8-fold greater for iron dextran and ferumoxytol than for iron sucrose." The study covered five products and not ferric derisomaltose, reported no outside funding, and its authors noted that the results may not apply to people outside Medicare.[33]

In a double-blind trial of 1,997 adults with iron deficiency anemia, moderate to severe allergic reactions or low blood pressure occurred in 0.6% of people given ferumoxytol and 0.7% of people given ferric carboxymaltose, and no anaphylaxis was reported in either group; the trial was sponsored by AMAG Pharmaceuticals, a maker of ferumoxytol.[26][27] The Injectafer, Monoferric and Feraheme labels each say that side effect rates seen in one product's clinical trials cannot be directly compared with rates from other trials, so label figures do not show which product has fewer allergic reactions.[12][13][24] The six IV iron prescribing-information labels we reviewed each warn of serious hypersensitivity reactions, so none of them supports calling its product free of allergic reactions.[12][13][24][30][31][32]

Low blood phosphate

Hypophosphatemia means a low level of phosphate in the blood.[25]

Since August 2026, the Injectafer prescribing information has carried a boxed warning about low blood phosphate (hypophosphatemia). It says Injectafer 'can cause severe, prolonged hypophosphatemia associated with serious outcomes, including hospitalization, osteomalacia and fractures requiring clinical intervention'. The label says to check phosphate levels before a repeat course in patients at risk of low phosphate and in anyone having a repeat course within three months. The Injectafer label says that in most cases low blood phosphate resolved within three months.[12]

In two identically designed open-label trials of 245 US adults with iron deficiency anemia who could not tolerate or did not respond to iron tablets, blood phosphate fell below 2.0 milligrams per deciliter within 35 days in 7.9% and 8.1% of people given ferric derisomaltose and in 75.0% and 73.7% of people given ferric carboxymaltose.[25] The two phosphate trials were sponsored by Pharmacosmos, the maker of ferric derisomaltose, and their authors wrote that "further research is needed to determine the clinical importance of this difference."[25][28][29] The Monoferric label reports blood phosphate below 2.0 milligrams per deciliter in 3.5% of people given Monoferric in two clinical trials, so ferric derisomaltose is not free of this effect.[13] In a separate trial of 1,997 adults sponsored by AMAG Pharmaceuticals, a maker of ferumoxytol, low blood phosphate was reported in 0.4% of people given ferumoxytol and 38.7% of people given ferric carboxymaltose; the trial's summary does not say how low phosphate was defined.[26][27] The Injectafer label reports blood phosphorus below 2 milligrams per deciliter, described as transient, in 27% of people in its clinical trials (440 of 1,638).[12] The Injectafer and Monoferric labels each say their trial rates are not directly comparable with rates from other clinical trials, so the two phosphate figures do not show which product lowers phosphate more.[12][13]

Skin staining from leakage

The Injectafer and Monoferric labels both warn that iron leaking out of the vein during an infusion can leave a brown discoloration of the skin that may be long lasting.[12][13] For leakage, the Injectafer and Monoferric labels give the same instruction: watch for it, and stop giving the product at that site if it occurs.[12][13] One Australian health service that reviewed its own incident reports from 2016 to 2022 counted 103 skin stains after IV iron, a rate of 0.31 stains per 100 infusions, and judged 86% of the stains preventable.[34] In the Australian audit, stopping the infusion as soon as leakage was noticed was associated with smaller stains.[34]

Other label warnings

The Feraheme label says the product may cause clinically significant low blood pressure.[24] According to the Feraheme label, the product may temporarily affect MRI scans, and the change may last for up to 3 months after the last dose.[24] The Injectafer and Feraheme labels say that for 24 hours after a dose, laboratory tests may overestimate the amount of iron in the blood.[12][24] The Injectafer label reports high blood pressure in 4% of people in two of its clinical trials (67 of 1,775) and short rises in blood pressure, sometimes with facial flushing, dizziness or nausea, in 6% (106 of 1,775).[12]

Anyone considering an iron infusion should go over these risks, and their own blood test results, with a licensed clinician.

Sources: Feraheme injection prescribing information, Revised 05/2026; Ferrlecit injection prescribing information, Revised 03/2022; INFeD injection prescribing information, Revised 08/2024; Injectafer injection prescribing information, Revised 08/2026; Monoferric injection prescribing information, Revised 08/2022; Venofer injection prescribing information, Revised 02/2026.

If you have severe symptoms, call 911 or seek emergency care. Report side effects to FDA MedWatch.

Contraindications in the labels we read

The Injectafer label says the product should not be given to people with a history of allergy (hypersensitivity) to Injectafer or its ingredients, and the Monoferric label says the same for a history of serious hypersensitivity to Monoferric; the Feraheme label names a known hypersensitivity to Feraheme or a history of allergic reaction to any intravenous iron product.[12][13][24]

Sources: Feraheme injection prescribing information, Revised 05/2026; Injectafer injection prescribing information, Revised 08/2026; Monoferric injection prescribing information, Revised 08/2022.

How an iron infusion is given

The Injectafer label describes a slow injection into a vein or an infusion over at least 15 minutes, the Monoferric label an infusion over at least 20 minutes, and both say to watch the person for signs of an allergic reaction for at least 30 minutes afterwards and until clinically stable.[12][13]

The Injectafer, Monoferric and Venofer labels each say to give the product only 'when personnel and therapies are immediately available' to treat serious allergic reactions. The Feraheme and Ferrlecit labels say the same for anaphylaxis and other allergic reactions. The INFeD label says to 'Have resuscitation equipment and personnel trained in the detection and treatment of anaphylactic-type reactions readily available during INFeD administration.'

For iron deficiency anemia in people who weigh 50 kg or more, the Injectafer label describes a course as two 750 mg doses at least 7 days apart or, for adults, a single dose of 15 mg per kg up to 1,000 mg, and the Monoferric label describes a single 1,000 mg dose.[12][13]

Dose schedules on this page summarize the Injectafer injection and Monoferric injection prescribing information and are not instructions to follow.

A prescriber sets and adjusts the dose.

Sources: Injectafer injection prescribing information, Revised 08/2026; Monoferric injection prescribing information, Revised 08/2022; Section 2 (Dosage and Administration) of each.

The labels we read give infusion or injection times and minimum observation times, and do not say how long a whole appointment takes.[12][13]

Sources: Feraheme injection prescribing information, Revised 05/2026; Ferrlecit injection prescribing information, Revised 03/2022; INFeD injection prescribing information, Revised 08/2024; Injectafer injection prescribing information, Revised 08/2026; Monoferric injection prescribing information, Revised 08/2022; Venofer injection prescribing information, Revised 02/2026.

Alternatives to an iron infusion

The main alternative to an iron infusion is iron taken by mouth: the British Society of Gastroenterology's 2021 guideline recommends one iron tablet a day as the first treatment for iron deficiency anemia and says that, if the tablet is not tolerated, one tablet every other day, a different oral iron product, or injected or infused iron should be considered.[1]

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