Is Ferrous Bisglycinate a Good Form of Iron? An In-Depth Analysis

December 11, 2025 •

5 min read

In recent years, ferrous bisglycinate has emerged as a popular alternative to traditional iron supplements, promising better tolerance and higher absorption rates. This chelated form of iron is often recommended for individuals who experience gastrointestinal issues with conventional iron salts.

Quick Summary

A guide exploring the advantages of ferrous bisglycinate, including its high bioavailability and minimal side effects, compared to other common iron preparations.

Key Points

Superior Absorption: Ferrous bisglycinate is chelated, which increases its bioavailability and effectiveness compared to standard iron salts.
Reduced Side Effects: The chelated structure minimizes the risk of common gastrointestinal issues like constipation and nausea.
Ideal for Sensitive Stomachs: Due to its gentle nature, ferrous bisglycinate is a top choice for individuals with digestive sensitivities.
Resists Inhibitors: This form is less affected by dietary factors like tannins and phytates, allowing for better absorption.
Better Adherence: Improved tolerance often leads to better patient compliance with the iron supplementation regimen.
Effective for Deficiency: Studies indicate it is highly effective in increasing hemoglobin and replenishing iron stores.

What is Ferrous Bisglycinate?

Ferrous bisglycinate is a form of iron supplement where a ferrous iron ion ($Fe^{2+}$) is bonded, or chelated, to two molecules of the amino acid glycine. This chelation process is key to its benefits. Instead of being an inorganic salt like ferrous sulfate, the iron is protected within the amino acid structure. This creates a more stable compound that is less likely to react with dietary inhibitors in the stomach and intestines, which can interfere with absorption. The chelated molecule is also more easily transported across the intestinal wall, allowing for more efficient uptake by the body.

The Science of Chelation

Chelation essentially acts as a protective shield for the mineral. For iron, this means the ferrous bisglycinate molecule can pass through the digestive system largely intact, preventing the iron from being released prematurely. This reduces the amount of unabsorbed iron that can cause gastrointestinal distress, and it also prevents the iron from binding to other compounds like phytates and tannins, which are known to inhibit non-heme iron absorption.

Why is Ferrous Bisglycinate a Good Form of Iron?

Ferrous bisglycinate is widely regarded as a superior form of iron for several reasons, primarily due to its enhanced bioavailability and gentler effect on the digestive system.

Enhanced Absorption and Bioavailability

Multiple studies have shown that ferrous bisglycinate is more effectively absorbed than other iron supplements, particularly ferrous sulfate. Its stable structure allows it to avoid common inhibitors and be absorbed through a different pathway than conventional iron salts. For people with compromised digestive function or low stomach acid, this can be particularly beneficial. This improved absorption can lead to more efficient replenishment of iron stores, often at a lower dosage than required with other forms.

Fewer Gastrointestinal Side Effects

One of the most significant advantages of ferrous bisglycinate is its excellent tolerability. Traditional iron salts, such as ferrous sulfate, frequently cause unpleasant side effects like constipation, nausea, and stomach upset. The chelated nature of ferrous bisglycinate means less unabsorbed iron is left in the intestine to cause irritation, leading to better patient compliance and a more comfortable experience for those needing long-term supplementation.

Better Patient Compliance

Because ferrous bisglycinate is associated with fewer digestive issues, patients are more likely to stick with their prescribed treatment regimen. Poor tolerability is a major reason why many people fail to complete iron therapy, which can compromise the effectiveness of treatment for iron deficiency anemia. The improved side-effect profile of bisglycinate addresses this problem directly.

Comparing Iron Supplement Forms


Feature	Ferrous Bisglycinate	Ferrous Sulfate	Ferrous Fumarate	Ferrous Gluconate
Absorption Rate	High, up to 4x higher than sulfate	Moderate to Low	Moderate to High	Moderate
Gastrointestinal Side Effects	Low; minimal constipation, nausea	High; common constipation, nausea, upset stomach	Moderate to High; bloating, constipation	Low; gentler on stomach than sulfate
Chelated?	Yes, amino acid chelate	No, inorganic salt	No, inorganic salt	No, inorganic salt
Effect on Iron Stores	Effective at increasing ferritin levels	Can increase ferritin, but may require higher doses	Effective at increasing iron levels	Generally effective
Cost	Typically more expensive	Very affordable	Affordable	Affordable
Absorption Inhibitors	Resistant to phytates, tannins	Inhibited by phytates, tannins, calcium	Inhibited by dietary factors	Inhibited by dietary factors

How to Maximize Iron Bisglycinate Absorption

Even with a highly bioavailable form like ferrous bisglycinate, there are steps you can take to ensure you get the most out of your supplement.

Combine with Vitamin C: Although less critical than with other iron forms, Vitamin C can still enhance iron absorption. Taking your supplement with a glass of orange juice or a vitamin C-rich food can be beneficial.
Consider Optimal Timing: While it can be taken with food, taking ferrous bisglycinate on an empty stomach often yields the best absorption. If you experience any stomach discomfort, taking it with a meal is a good compromise.
Avoid Calcium and Other Inhibitors: While ferrous bisglycinate is more resistant to inhibitors, large amounts of calcium, tannins (found in tea and coffee), or phytates (in legumes and grains) can still impact absorption. It's best to separate the intake of these items by at least two hours.

Potential Side Effects and Precautions

While significantly better tolerated, ferrous bisglycinate is not entirely without potential side effects. Some individuals may still experience mild digestive issues such as nausea, bloating, or changes in bowel movements. Dark stools are a harmless and common side effect of any oral iron supplement. It is crucial to consult a healthcare provider before starting any iron supplement, as excessive iron intake can be harmful.

It's important to remember that supplements are not regulated like drugs and product quality can vary. Look for reputable brands that offer third-party testing to ensure the product's purity and potency. A trusted source like the National Institutes of Health provides reliable information on iron supplementation. For more detailed information on iron and its functions, refer to their fact sheet on the topic: Iron - Health Professional Fact Sheet.

Conclusion

Ferrous bisglycinate is an excellent form of iron supplementation, particularly for those with sensitive stomachs or poor absorption. Its chelated structure offers higher bioavailability and a reduced risk of gastrointestinal side effects compared to older, more conventional iron salts like ferrous sulfate. While generally more expensive, the benefits of improved absorption and tolerance make it a worthwhile investment for many individuals with iron deficiency. As with any supplement, consulting a healthcare professional is recommended to determine the right dosage and duration for your specific health needs.

How It Works

Chelated Form: The iron is bonded to the amino acid glycine, protecting it from dietary inhibitors and allowing for superior absorption.
Gentle on the Stomach: Due to its protective chelation, less unabsorbed iron irritates the digestive tract, minimizing common side effects.
Higher Bioavailability: Studies show ferrous bisglycinate is absorbed more efficiently than inorganic iron salts, meaning you may need a lower dose.
Regulated Absorption: The body's iron status influences how much ferrous bisglycinate is absorbed, which may reduce the risk of overload.
Improved Compliance: Better tolerance leads to more consistent usage, which is crucial for effectively treating iron deficiency over time.

Frequently Asked Questions

Ferrous bisglycinate is a chelated form where iron is bound to the amino acid glycine, resulting in superior absorption and fewer side effects. Ferrous sulfate is a traditional, unchelated inorganic salt that is less bioavailable and more likely to cause gastrointestinal distress.

Ferrous bisglycinate is significantly less likely to cause constipation and other digestive side effects compared to non-chelated iron supplements. However, mild gastrointestinal discomfort is still possible, depending on individual sensitivity and dosage.

Yes, ferrous bisglycinate is often recommended for pregnant women. Its high tolerability and effectiveness make it a preferred option for treating or preventing iron deficiency anemia during pregnancy, which is very common.

While individual results vary, many people begin to feel an improvement in energy levels and overall well-being within a few weeks of consistent use. Replenishing iron stores fully can take several months, so it is important to continue the regimen as advised by a healthcare provider.

Yes, studies have shown that ferrous bisglycinate is both safe and effective for treating iron deficiency anemia in children, often with better results than ferrous sulfate. It is important to follow a pediatrician's guidance on dosage.

While ferrous bisglycinate is less affected by inhibitors than other iron forms, it is still best to avoid taking it at the same time as large amounts of calcium (dairy products), tea, coffee, or high-fiber foods. It's recommended to wait at least two hours between consumption.

Generally, yes. Because of the chelation process, ferrous bisglycinate is typically more expensive than simple iron salts like ferrous sulfate. However, the superior absorption and reduced side effects are often considered worth the additional cost.

Heme iron, found in animal products, is the most readily absorbed form of iron. Ferrous bisglycinate is a highly bioavailable form of non-heme iron that can be absorbed more efficiently than other non-heme sources, making it a powerful supplement, especially for vegetarians and vegans.