Supplement analysis backed by scientific evidence · PT

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Moderate evidenceVitamins & minerals

Iron Bisglycinate

The one premium iron form with a real meta-analysis behind it: in pregnant women it raised haemoglobin more than conventional iron salts and cut gastrointestinal side effects by roughly two thirds. In children the same analysis found no advantage, so the benefit is population-specific rather than universal.

What the science says

  • Higher haemoglobin and fewer GI side effects in pregnancy Moderate evidence

    A systematic review and meta-analysis of 17 RCTs found that in pregnant women, 4-20 weeks of ferrous bisglycinate produced higher haemoglobin than other iron supplements (SMD 0.54 g/dL, 95% CI 0.15-0.94) and fewer gastrointestinal adverse events (incidence rate ratio 0.36, 95% CI 0.17-0.76). Tolerability is the more reliable of the two benefits and the one that matters most for adherence.

  • No demonstrated advantage in children, and ferritin gains were not significant Limited evidence

    In the same meta-analysis, the four paediatric trials showed no significant difference in haemoglobin or ferritin versus other iron supplements, and the ferritin trend in pregnant women did not reach significance. Iron stores — the outcome that determines whether treatment actually worked — remain the weakest part of the case.

  • Comparable results at lower elemental doses, but the evidence base is modest Limited evidence

    Trials commonly matched 25-30 mg elemental iron as bisglycinate against 60-100 mg as ferrous sulfate, which is where the tolerability advantage largely comes from. An independent 2024 review of oral iron formulations concluded that the comparative trial evidence for newer formulations is limited and that superiority over cheap iron salts is not established; a 2012 trial in cancer patients with mild anaemia is typical — positive, but small.

Dosage & safety

Studied dose14-30 mg elemental iron per day for treatment or repletion of iron deficiency; ferrous bisglycinate is roughly 20% elemental iron, so a 100 mg salt dose supplies about 20 mg elemental. Alternate-day rather than daily dosing improves fractional absorption by blunting the hepcidin response and is increasingly preferred. Take away from tea, coffee, calcium and dairy; vitamin C is not required with bisglycinate the way it helps with sulfate.
SafetyConstipation, dark stools and nausea still occur, though less often than with ferrous sulfate. Iron overdose is one of the leading causes of fatal poisoning in young children — keep bottles closed and out of reach. Contraindicated in hereditary haemochromatosis and other iron-overload states; do not supplement iron without a confirmed ferritin or haemoglobin indication. Iron reduces absorption of levothyroxine, tetracyclines, quinolones, bisphosphonates and levodopa (separate by 2-4 hours), and proton pump inhibitors reduce iron absorption. Not banned in sport.

Scientific references

Where to buy

Thorne, Iron Bisglycinate, 60 Capsules (25 mg per Capsule)

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