Home Ingredients Ferrous Bisglycinate
Bone HealthImmune Support

Ferrous Bisglycinate

Evidence Level
Strong
2 Clinical Trials
5 Documented Benefits
4/5 Evidence Score

Ferrous bisglycinate is iron chelated with two glycine molecules — a newer form distinguished by superior tolerability vs ferrous sulfate while maintaining good absorption. Meta-analyses show iron bisglycinate is more effective than other iron salts for raising hemoglobin in pregnant women, with significantly fewer GI side effects. Particularly valuable for pregnancy, IBD, or any patient who cannot tolerate sulfate.

Studied Dose 25-60 mg elemental iron/day; pregnancy: 25-30 mg/day often sufficient
Active Compound Ferrous bisglycinate (Fe-bisglycinate chelate)

Benefits

Superior GI Tolerability

Iron bisglycinate causes substantially fewer GI side effects than ferrous sulfate — less constipation, nausea, and gastric pain. Rate of patients quitting therapy is much lower. Critical advantage for chronic supplementation, pregnancy, and IBD populations.

Supported by Trial 2, Trial 1

Better Absorption Than Sulfate

Some research suggests ferrous bisglycinate is up to 4× more bioavailable than ferrous sulfate; meta-analysis showed iron bisglycinate more effective than other salts for raising hemoglobin in pregnant women.

Supported by Trial 1

Resistance to Absorption Inhibitors

The chelate structure protects iron from common absorption inhibitors — phytates (in cereals/grains), oxalates (in spinach), polyphenols (in coffee/tea). Means more reliable absorption when taken with meals.

Supported by Trial 1

Pregnancy Iron Supplementation

Pregnancy iron requirements increase substantially (RDA 27 mg/day vs 18 mg pre-pregnancy). Ferrous bisglycinate's tolerability is particularly valuable when nausea/morning sickness already strain GI comfort.

Supported by Trial 2, Trial 1

IBD/Crohn's/Ulcerative Colitis

Inflammatory bowel disease patients often have iron deficiency but cannot tolerate ferrous sulfate (worsens GI symptoms, may aggravate inflammation). Bisglycinate is gentler alternative for these populations.

Supported by Trial 2, Trial 1

Mechanism of action

1

Glycine Chelate Stability

Iron ion bonded to two glycine molecules in stable chelate. Resists gastric pH changes and competing absorption inhibitors. Absorbed via standard iron transport (DMT1) AND potentially via dipeptide transporters as an intact glycine complex.

2

Reduced Free Iron in GI Tract

Free Fe²⁺ in GI tract generates reactive oxygen species that damage mucosal cells — basis for ferrous sulfate's GI symptoms. Chelated bisglycinate keeps iron bound through transit, reducing free-iron-mediated mucosal damage.

3

Bypass of Absorption Inhibitors

Phytates and polyphenols bind free iron and reduce absorption — but cannot displace iron from the bisglycinate chelate. Iron arrives at duodenal absorption sites still bound and intact.

4

Standard Iron Functions

Once absorbed, iron functions identically regardless of supplemental form — incorporated into hemoglobin (oxygen transport), myoglobin (muscle oxygen storage), cytochromes (electron transport), iron-sulfur cluster enzymes.

Clinical trials

1
Iron Bisglycinate for Pregnancy IDA

Pooled analysis comparing iron bisglycinate vs other iron salts for IDA treatment in pregnant women.

Pooled across pregnancy IDA clinical trials.

Iron bisglycinate was significantly MORE effective than other iron salts (sulfate, fumarate) at raising hemoglobin in pregnant women, with SIGNIFICANTLY FEWER GI side effects. Important comparative evidence supporting bisglycinate as preferred form for pregnancy IDA.

2
Ferrous Bisglycinate Tolerability vs Sulfate — Clinical Trial

Multiple clinical trials comparing ferrous bisglycinate vs ferrous sulfate for tolerability and adherence in IDA patients.

Pooled across tolerability trials.

Ferrous bisglycinate causes substantially fewer GI side effects (constipation, nausea, abdominal pain) vs ferrous sulfate. Adherence rates higher. Supports bisglycinate as preferred form for tolerability-sensitive populations.

Side effects and drug interactions

Common Potential side effects

Generally much better-tolerated than ferrous sulfate.
Mild GI distress at high doses.
Constipation — less common but still possible.
Dark stools — expected, harmless.
Metallic taste rare with chelate form.
PEDIATRIC IRON POISONING — same caution as all iron forms; child-resistant packaging mandatory.

Important Drug interactions

Same general iron interactions: tetracyclines, quinolones, levothyroxine, bisphosphonates, levodopa — separate by 2-4 hours.
Calcium — competes for absorption; separate dosing.
PPIs/antacids — reduce iron absorption.
Vitamin C — enhances absorption.
Coffee/tea tannins — chelation protection means LESS interference than with sulfate, but still recommend separation.

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Frequently asked questions about Ferrous Bisglycinate

What is ferrous bisglycinate?

Ferrous bisglycinate is iron chelated to the amino acid glycine. It is well absorbed and notably gentler on the stomach than ferrous sulfate, making it a popular choice for people who get side effects from standard iron.

Is ferrous bisglycinate easier on the stomach?

Yes, that is its main advantage. The chelated structure causes less constipation, nausea, and cramping than ferrous sulfate, so it suits those who cannot tolerate conventional iron. It also tends to cause less of the dark-stool effect.

How much ferrous bisglycinate should I take?

Because it is well absorbed, effective doses are often lower than with ferrous sulfate, commonly around 25 to 50 mg of elemental iron, sometimes every other day. Only take iron for a confirmed deficiency, ideally with medical guidance.

How can I absorb ferrous bisglycinate better?

Take it with vitamin C and away from coffee, tea, dairy, and calcium. It is gentle enough that many tolerate it on an empty stomach, which maximizes absorption. Every-other-day dosing can improve overall uptake.

What is Ferrous Bisglycinate used for?

Ferrous Bisglycinate is researched primarily for Bone Health and Immune Support. Iron bisglycinate causes substantially fewer GI side effects than ferrous sulfate — less constipation, nausea, and gastric pain. Rate of patients quitting therapy is much lower.

What is the recommended dosage of Ferrous Bisglycinate?

The clinically studied dose is 25-60 mg elemental iron/day; pregnancy: 25-30 mg/day often sufficient Always follow the product label and check with a healthcare provider for personal advice.

Is Ferrous Bisglycinate safe, and does it have side effects?

For most healthy adults, Ferrous Bisglycinate is well tolerated at studied doses. Reported effects can include: Generally much better-tolerated than ferrous sulfate. Mild GI distress at high doses. It may also interact with some medications. Ferrous Bisglycinate is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Ferrous Bisglycinate interact with any medications?

Possible interactions include: Same general iron interactions: tetracyclines, quinolones, levothyroxine, bisphosphonates, levodopa — separate by 2-4 hours. Calcium — competes for absorption; separate dosing. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Ferrous Bisglycinate?

NutraSmarts rates the evidence for Ferrous Bisglycinate as Strong (4 out of 5). It is backed by 2 clinical trials and 4 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(4 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Milman N, Jonsson L, Dyre P, Pedersen PL, Larsen LG. Ferrous bisglycinate 25 mg iron is as effective as ferrous sulfate 50 mg iron in the prophylaxis of iron deficiency and anemia during pregnancy in a randomized trial. J Perinat Med. 2014;42(2):197-206. doi: 10.1515/jpm-2013-0153.PubMedUsed to support: Randomized pregnancy trial showing chelated ferrous bisglycinate at half the elemental-iron dose matched ferrous sulfate for preventing iron deficiency/anemia - supports reasonable bioavailability and effectiveness at lower doses, consistent with a gentler chelated form.
  2. Ferrari P, Nicolini A, Manca ML, Rossi G, Anselmi L, Conte M, et al. Treatment of mild non-chemotherapy-induced iron deficiency anemia in cancer patients: comparison between oral ferrous bisglycinate chelate and ferrous sulfate. Biomed Pharmacother. 2012;66(6):414-8. doi: 10.1016/j.biopha.2012.06.003.PubMedUsed to support: RCT comparing ferrous bisglycinate with ferrous sulfate, reporting comparable efficacy with fewer gastrointestinal side effects for the bisglycinate chelate - supports the better-tolerability claim, while noting this is a small single trial in a specific population.
  3. Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2023;81(8):904-920. doi: 10.1093/nutrit/nuac106.PubMedUsed to support: Systematic review and meta-analysis of bisglycinate RCTs - the honest evidence-synthesis anchor: bisglycinate raises hemoglobin/ferritin and is a viable option, but data are limited and heterogeneous and do not establish clear superiority over cheap ferrous sulfate.
  4. Stoffel NU, Zeder C, Brittenham GM, Moretti D, Zimmermann MB. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica. 2020;105(5):1232-1239. doi: 10.3324/haematol.2019.220830.PubMedUsed to support: RCT showing alternate-day dosing improves fractional iron absorption (via lower hepcidin) versus daily dosing - supports the emerging dosing strategy that, for any oral iron form including bisglycinate, alternate-day dosing can enhance absorption and may reduce side effects.