Benefits
Absorbed by a Different Route Than Iron Salts
Heme iron enters the duodenal cell with the iron still inside its porphyrin ring rather than as free ferrous iron, so the phytates in grains and the polyphenols in tea and coffee that block ferrous salts have little effect on it. The carrier was originally named HCP1 (heme carrier protein 1), but the same gene product was shown in 2006 to work mainly as the intestinal proton coupled folate transporter, and the human heme importer has still not been identified. Calcium is not bypassed: in a study of 126 people, 165 mg of calcium given as milk, cheese or calcium chloride significantly reduced heme iron absorption as well as non-heme iron absorption.
Larger Short Term Serum Iron Rise When Taken with Food
The direct comparison is a 14 person crossover published in Nutrition Research in 2000: 20 mg of iron as heme iron polypeptide taken with breakfast produced a larger rise in serum iron over 6 hours than 20 mg as ferrous fumarate (p<0.03). That study is small, it has never been independently replicated, and the journal it appeared in is not indexed in MEDLINE. The 2025 infant trial found the same pattern on blood markers, with 48 percent higher serum iron and 52 percent higher transferrin saturation on heme iron. That short term marker advantage did not carry through to the outcomes that decide whether anemia gets better: hemoglobin and ferritin were no different from ferrous sulfate.
Fewer Reported Side Effects, on Weak Evidence
Pooling 13 randomized trials, people given heme iron reported 38 percent fewer total side effects than people given non-heme iron (RR 0.62, 95 percent CI 0.40 to 0.96). The reviewers graded that result very low certainty and noted that most of the trials gave heme iron in low doses combined with non-heme iron, often at a lower total iron dose, and a lower iron dose on its own reduces gut symptoms. In the largest single trial, 208 anemic infants on 10 mg/day, adverse events occurred at the same rate on heme iron and on ferrous sulfate.
Less Dependent on Stomach Acid, But Not Calcium Proof
Heme iron does not have to be freed from a salt by stomach acid, so acid suppressing drugs are expected to interfere with it less than they do with ferrous sulfate. That is a mechanistic expectation: no trial has compared heme iron with a ferrous salt in people taking proton pump inhibitors. Coffee and tea polyphenols do have little effect on it. Calcium is the real exception and should not be lumped in with them, because calcium significantly reduces heme iron absorption in humans.
Where It Has Actually Been Tested
Randomized testing of heme iron polypeptide has been done in peritoneal dialysis patients, in non-dialysis chronic kidney disease, in women after Roux-en-Y gastric bypass, and in anemic infants. The gastric bypass trial is the one people cite this product for, and it went the other way: the researchers stopped it early because ferrous sulfate raised hemoglobin from 10.8 to 13.0 g/dL and ferritin from 4.9 to 15.5 ug/L while heme iron changed none of the iron markers. It has never been tested in inflammatory bowel disease, and it has never been tested in people taking proton pump inhibitors.
Mechanism of action
Intact Heme Uptake, Then Release Inside the Cell
Heme is taken up intact across the apical membrane of the duodenal cell, and once inside, heme oxygenase 1 opens the porphyrin ring and frees the iron, which then leaves the cell through ferroportin exactly as iron from a ferrous salt does. The transporter that carries heme in has not been identified in humans. The candidate proposed in 2005 and called HCP1 turned out to be the intestinal proton coupled folate transporter, so any claim built on a named heme transporter is running ahead of the evidence.
Bypass of Iron Absorption Inhibitors
Phytate from grains and legumes, polyphenols from tea and coffee, and oxalates all cut absorption of non-heme iron. Because heme reaches the gut wall with the iron still locked in its ring, those three have much less grip on it. Calcium does not belong on that list: it reduces heme iron absorption too, which points to the block being at the transfer step inside the cell rather than in the gut lumen.
Animal Source Polypeptide Matrix
HIP is made by enzymatically digesting hemoglobin from slaughterhouse blood, leaving heme still attached to short peptides. Proferrin is refined from bovine blood; other heme iron ingredients are made from porcine blood, and heme iron has also been produced from fish blood. It is chemically the same form of iron found in red meat, which is why the marketing borrows the absorption figures for dietary heme. Those figures come from meat in a meal, not from this tablet.
Reduced Mucosal Irritation
Less free ferrous iron sitting in the gut lumen should mean less oxidative irritation of the gut lining, which is the proposed reason for better tolerability. The human evidence for that is thin: pooled trials show a 38 percent reduction in reported side effects at very low certainty, while the largest single trial found no difference in adverse events at all.
Clinical trials
Bah M, Verhoef H, Okoh E, et al. Am J Clin Nutr 2025;122(4):997-1005. PMID 40803493. Randomized, 84 days of directly observed daily supplementation with 10 mg elemental iron as heme iron polypeptide or as ferrous sulfate. Adherence about 90 percent.
208 anemic infants aged 6 to 12 months in The Gambia (hemoglobin 7.0 to under 11.0 g/dL).
Hemoglobin and ferritin improved in both groups by day 84 with no difference between treatments, and the authors concluded there is no benefit of heme iron on those endpoints. Anemia prevalence fell from 83.7 to 46.2 percent on ferrous sulfate and from 84.6 to 47.1 percent on heme iron. Heme iron did produce higher serum iron (by 48.4 percent) and higher transferrin saturation (by 52.3 percent). Adverse events occurred at the same rate in both groups.
Mischler RA, Armah SM, Craig BA, et al. Obes Surg 2018;28(2):369-377. PMID 28779269. Randomized, single blind, 8 weeks of ferrous sulfate 195 mg/day or heme iron polypeptide 31.5 to 94.5 mg/day. Compliance above 94 percent. The trial was stopped early.
14 iron deficient women an average of 6.9 years after Roux-en-Y gastric bypass (6 on ferrous sulfate, 8 on heme iron).
On ferrous sulfate, hemoglobin rose from 10.8 to 13.0 g/dL, ferritin from 4.9 to 15.5 ug/L and soluble transferrin receptor fell from 2111 to 1270 ug/L, all p<0.0001. On heme iron polypeptide, no iron status marker changed. The investigators stopped the trial early because of the size of the difference and concluded that ferrous sulfate, but not heme iron, corrected iron deficiency after this surgery. With 14 participants the trial is small, and it does not tell you how heme iron performs in people with normal gut anatomy.