Know2eat

Iron bisglycinate

Minerals

What iron bisglycinate may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedIron statusModerate evidence· 4 sources

Then, in order

About Iron bisglycinate

Iron chelated to two glycine molecules, supplying about 20% elemental iron. It is marketed as a gentler alternative to ferrous sulfate, on the argument that the chelate stays intact through the stomach and irritates less.

Iron bisglycinate is a legitimate alternative with a modest and somewhat inconsistent evidence base. Several trials report fewer gastrointestinal side effects than ferrous sulfate at comparable elemental doses, and some suggest equal or better absorption at lower doses, which is a reasonable basis for choosing it when sulfate is intolerable. The evidence is not strong enough to call it superior: trials are small, comparisons use different elemental doses, and ferrous sulfate remains the reference in most treatment guidelines because it is cheap and its behaviour is thoroughly characterised. The important cautions — children, haemochromatosis, deficiency needing a diagnosis — are identical.

Sold as
Capsule, Tablet, Liquid, Component of prenatal and gentle-iron products
Also known as
Ferrous bisglycinate, Chelated iron, Gentle iron

Regulation: Covered by the same 45 mg/day Tolerable Upper Intake Level for elemental iron and by the same mandatory child-poisoning warning on iron-containing supplements in the US.

What the research used

The amounts, forms and durations published trials of Iron bisglycinate actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Typical retail supplement

    18–28 mg

    Limited

    Elemental iron, daily

    Lower elemental doses than typical ferrous sulfate regimens, which is part of why side effects are fewer. Whether it corrects deficiency as quickly at those doses is less well established.

  • Studied for Comparative trials against ferrous sulfate

    25–60 mg

    Moderate

    Elemental iron, daily · 6 weeks–6 months

    Trials in pregnancy and in iron deficiency report similar haemoglobin responses with fewer gastrointestinal complaints, but sample sizes are small and elemental doses often differ between arms, which complicates interpretation.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

Each timing below was actually compared against an alternative in a trial, which is unusual.

  • On an empty stomach

    Moderate

    Absorption is better away from food, though bisglycinate appears less affected by food and by phytate than ferrous sulfate in absorption studies — one of the more credible advantages claimed for it.

    Timing was tested. A trial compared this window against another and reported a difference.

  • Any time

    Moderate

    Still best separated from calcium supplements, dairy, tea and coffee, all of which reduce iron absorption. Vitamin C taken alongside increases it.

    Timing was tested. A trial compared this window against another and reported a difference.

The evidence in depth

Best supported: Moderate

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Iron status

Women's Health
Moderate evidence

Trials find iron bisglycinate raises haemoglobin and ferritin comparably to ferrous sulfate, often at lower elemental doses and with fewer gastrointestinal complaints. The trials are smaller and fewer than those behind ferrous sulfate, which is why guidelines still name sulfate first.

Moderate evidence. Several human studies point the same way, with real caveats.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Digestive comfort

Gut & Digestive Health
Limited evidence

Several comparative trials report fewer reports of nausea, constipation and abdominal pain than with ferrous sulfate. Because the elemental doses often differ between study arms, some of that difference may simply be less iron.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Pregnancy nutrition

Women's Health
Limited evidence

Trials in pregnancy report comparable haemoglobin outcomes to ferrous sulfate with better tolerance, which matters when nausea already limits adherence. The trials are small and mostly from single centres.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Too much

    Child poisoning risk is unchanged

    A gentler iron on an adult stomach is exactly as dangerous to a toddler who eats a bottle of it. Iron remains a leading cause of fatal poisoning in young children; storage out of reach and immediate poison-centre contact after ingestion apply identically.

  • Avoid

    Haemochromatosis and iron overload

    Any iron supplement accelerates iron accumulation in hereditary haemochromatosis or transfusional overload. Iron studies before starting, particularly in men and postmenopausal women, are the sensible precaution.

  • Worth knowing

    Deficiency still needs investigating

    Unexplained iron deficiency warrants a search for a cause — gastrointestinal blood loss and coeliac disease among them. Choosing a better-tolerated iron does not change that.

  • Interaction

    Same medicine interactions

    Interacts withLevothyroxine, tetracyclines, fluoroquinolones, bisphosphonates, levodopa, proton pump inhibitors

    Reduces absorption of levothyroxine, tetracyclines, fluoroquinolones, bisphosphonates and levodopa; acid-suppressing drugs reduce iron absorption in turn.

  • Worth knowing

    Cost and elemental content

    Bisglycinate costs several times more than ferrous sulfate, and labels sometimes state the chelate weight rather than elemental iron, making products look stronger than they are.

Evidence ratings on this page: 1 moderate evidence, 2 limited evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take Iron bisglycinate, or a dose to follow.