Magnesium Forms Compared: Glycinate, Citrate, Threonate
Absorption and tolerability differ meaningfully between salts. A practical comparison of the forms with human data behind them.
Why magnesium matters
Magnesium is a cofactor in more than 300 enzymatic reactions, including energy production, muscle contraction, nerve signaling, and blood pressure regulation. Dietary surveys suggest that a significant portion of adults fall short of recommended intakes, especially with modern processed-food diets.
Supplementation can help, but not all magnesium salts are equivalent. Absorption, tolerability, and tissue distribution vary widely between forms.
Glycinate, citrate, and threonate
Magnesium glycinate is a chelated form bound to the amino acid glycine. It tends to be well absorbed and gentle on the stomach, making it a good choice for general supplementation and sleep support.
Magnesium citrate is also well absorbed but has an osmotic effect that can loosen stools. It is useful for people with constipation, but may cause diarrhea at higher doses. Magnesium threonate is a newer form with animal data suggesting better brain penetration; human clinical data is still emerging.
What to look for
Elemental magnesium — the actual magnesium content, not the total weight of the salt — is what matters on the label. A product may advertise 500 mg of magnesium oxide but deliver only 300 mg of elemental magnesium, with much lower absorption than a chelated form.
For most adults, 200–400 mg of elemental magnesium per day from a well-absorbed form is a reasonable target. Taking it in the evening may support sleep and muscle relaxation. Avoid magnesium oxide if absorption is the priority; it is cheap but poorly bioavailable.
References
- Cazzola R, et al. Going to the roots of reduced magnesium dietary intake. Nutrients. 2020.
- Walker AF, et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research. 2003.
Disclaimer: This article is for educational purposes only. People with kidney disease should consult a clinician before taking magnesium supplements.