Does Magnesium Bisglycinate Interfere with Iron Absorption?

October 31, 2025 •

4 min read

While both iron and magnesium are vital minerals, their absorption can be influenced by several factors. For individuals taking supplements, a common question arises: does magnesium bisglycinate interfere with iron absorption? The answer is more nuanced than a simple yes or no, depending on timing and dosage.

Quick Summary

This article explores the interaction between magnesium bisglycinate and iron absorption. While certain magnesium forms can impede iron uptake, the chelated bisglycinate version is better tolerated. Proper timing is crucial to minimize any potential competitive absorption, especially at high doses.

Key Points

Timing is Key: Take magnesium bisglycinate and iron supplements at least two hours apart to minimize potential competition for absorption.
Bisglycinate is a Better Choice: As a chelated mineral, magnesium bisglycinate is generally less likely to interfere with iron absorption compared to other forms like magnesium oxide.
Vitamin C is an Iron Enhancer: Pairing your iron supplement with vitamin C can significantly increase its absorption, counteracting the effects of some inhibitors.
Listen to Your Body: If you experience digestive discomfort, separating your doses of magnesium and iron is a wise move.
Mind Other Inhibitors: Be aware that other factors like high-dose calcium, coffee, and tea can also inhibit iron absorption, so adjust your intake accordingly.
Inorganic vs. Organic Forms: Inorganic mineral salts are less bioavailable than organic, chelated forms, making the form of your supplement a critical factor in absorption.

Understanding Mineral Absorption

The Importance of Bioavailability

Bioavailability is the degree to which a nutrient is absorbed by the body and becomes available for use. This is a critical consideration when taking mineral supplements, as various factors can enhance or inhibit absorption. In the case of iron and magnesium, the digestive tract serves as the primary site of absorption, where different chemical forms of minerals and the presence of other nutrients can play a significant role.

Iron is absorbed primarily in the small intestine, and its absorption can be enhanced by vitamin C but inhibited by compounds like phytates and calcium. Magnesium is also absorbed in the intestines, but its absorption can be influenced by dietary fiber and vitamin D. The form of the supplement—whether organic (like bisglycinate) or inorganic (like oxide)—also dictates how well the body can use it.

Bisglycinate vs. Other Magnesium Forms

Magnesium supplements come in a variety of forms, and not all are created equal. In fact, the form of magnesium is a key factor in whether it will interact with iron absorption. Magnesium bisglycinate is a chelated form where magnesium is bound to the amino acid glycine. This creates a more stable, electrically neutral molecule that is highly bioavailable and gentle on the stomach.

In contrast, inorganic forms like magnesium oxide are less soluble and can have a more pronounced effect on stomach acidity. Studies have shown that excessive use of magnesium oxide, often in laxative preparations, can decrease stomach pH and form polymers that interfere with iron absorption, leading to cases of refractory iron-deficiency anemia. With magnesium bisglycinate, this type of interference is far less likely due to its chelated nature.

The Potential for Interference

While magnesium bisglycinate itself is not known to be a potent inhibitor of iron absorption, the potential for competition between minerals in the gut remains, especially at high doses. Both minerals use similar pathways for absorption to some extent, and flooding the system with a large dose of any mineral could potentially reduce the absorption of another. This is less of a concern with chelated forms like bisglycinate because they have high bioavailability and tend to be absorbed more efficiently, with less unabsorbed mineral left to cause issues.

How Proper Timing Prevents Issues

The best way to address the potential for competitive absorption is to time your supplements strategically. Experts recommend separating the intake of iron and magnesium by at least two hours. This allows the body to process each mineral separately and maximize its absorption. Many people find it beneficial to take iron in the morning and magnesium in the evening.

Morning Iron: Iron is often more energizing for some people. Taking it on an empty stomach can increase absorption, though this can sometimes cause stomach upset. If so, taking it with a small amount of food (and a source of vitamin C) is recommended.
Evening Magnesium: Magnesium is known for its calming and relaxing properties, which can help promote better sleep. Taking it with food can also minimize any potential digestive discomfort.

Comparison of Mineral Interactions

To better understand how supplements affect each other, here is a comparison table outlining the interactions between iron, magnesium, and other common minerals and nutrients.


Mineral/Nutrient	Interaction with Iron	Interaction with Magnesium
Magnesium (High Dose)	Potential for competitive inhibition, especially with high doses of inorganic forms like magnesium oxide. Minimal interference with bisglycinate when timed correctly.	Some evidence suggests iron supplementation might affect magnesium status, but the interaction is complex.
Calcium	Strongly inhibits the absorption of both heme and non-heme iron.	Can influence magnesium absorption, though the interaction is not fully understood.
Zinc	High doses of zinc can decrease iron absorption.	High doses of zinc can decrease magnesium absorption.
Vitamin C (Ascorbic Acid)	Significantly enhances the absorption of non-heme iron.	Can help activate vitamin D, which in turn aids magnesium absorption.
Phytates (in grains, legumes)	Potent inhibitor of non-heme iron absorption.	Excessive fiber and phytate intake can reduce magnesium absorption.

Practical Recommendations for Supplementation

To ensure you get the maximum benefit from both iron and magnesium bisglycinate, follow these best practices:

Time Your Doses: Separate the intake of iron and magnesium by at least two hours. For example, take your iron supplement in the morning and your magnesium bisglycinate in the evening.
Pair with Vitamin C: Take iron with a source of vitamin C (like orange juice or a vitamin C supplement) to significantly enhance its absorption, especially for plant-based iron.
Take with Food (if needed): While iron is best absorbed on an empty stomach, taking it with a small meal can help reduce stomach upset. Magnesium bisglycinate is generally well-tolerated and can be taken with or without food.
Avoid Known Inhibitors: When taking your iron supplement, avoid consuming dairy products, tea, and coffee, as they contain compounds that can inhibit iron absorption.
Monitor Effects: Pay attention to how your body responds. If you experience digestive issues or suspect reduced effectiveness, consult a healthcare provider to adjust your timing or dosage.

Conclusion

While the potential for interaction exists with some forms and high doses of magnesium, magnesium bisglycinate is a chelated, gentle form that is much less likely to interfere with iron absorption. By adhering to proper timing and dosage, you can effectively supplement both essential minerals to support overall health. Taking your iron supplement in the morning and magnesium bisglycinate in the evening is a simple yet effective strategy to ensure optimal bioavailability. As always, consult a healthcare provider before starting any new supplement regimen, especially if you have underlying health conditions or are taking other medications.

For more detailed information on nutrient interactions, the National Institutes of Health (NIH) Office of Dietary Supplements provides comprehensive fact sheets on both magnesium and iron.

Frequently Asked Questions

It is generally recommended to take iron and magnesium bisglycinate at separate times, at least two hours apart, to avoid any potential competition for absorption. A common approach is to take iron in the morning and magnesium in the evening.

Magnesium bisglycinate is a chelated, or organically bound, form of magnesium. It is highly bioavailable and less likely to cause the pH changes in the stomach that less absorbable inorganic forms like magnesium oxide can, which could interfere with iron absorption.

Taking iron and magnesium together, especially at high doses, might reduce the absorption of one or both minerals due to potential competition. For most people, lower doses are less problematic, but spacing out intake is still the best practice.

For optimal absorption and to minimize side effects, take your iron supplement in the morning, ideally on an empty stomach. Take magnesium bisglycinate in the evening to take advantage of its relaxing effects, especially if you also want to support better sleep.

Yes, vitamin C is a powerful enhancer of iron absorption, particularly for non-heme iron found in plant-based foods. Taking vitamin C with your iron supplement can help maximize its uptake.

To ensure maximum iron absorption, avoid taking calcium supplements, zinc supplements, and consuming coffee or tea at the same time as your iron supplement. These substances can inhibit iron uptake.

Some people may experience increased gastrointestinal side effects like nausea or diarrhea if they take both minerals at the same time. Spacing out doses can help mitigate these symptoms.

For individuals with mild needs, a multivitamin containing both might be fine. However, if you are treating a specific deficiency, particularly iron-deficiency anemia, it is often better to take separate supplements at different times for targeted and more effective absorption.