What is the best form of magnesium to take?

January 2021

People need many kinds of minerals for their bodies to work properly, including magnesium. Proteins called enzymes are vital for more than 300 important biological processes in the body. These include, for example, producing RNA and DNA molecules, regulating the levels of various nutrients, helping to prevent health conditions like osteoporosis and kidney disease, and making new proteins [11, 3, 13].

If you’re concerned that your diet is deficient in magnesium, taking a supplement is a safe way to increase your consumption. These supplements contain magnesium ions, which require a carrier that binds with the magnesium and carries it to the intestines. There, it is broken down and distributed by the blood throughout the body. Because different carriers dissolve at different rates, how much magnesium the body can absorb depends in part on the type of carrier in a given supplement, as well as the type of magnesium the supplement contains.

The Bottom Line

Magnesium glycinate is the best type of magnesium to take for most people because it is well-absorbed and has few, if any, gastrointestinal side effects. Magnesium citrate has high bioavailability as well, but it also has a laxative effect that you may or may not want. Magnesium oxide should be avoided because it is not absorbed well and is not very effective [2,10]. Whichever form you take, remember to always buy supplements from reputable manufacturers because they are not effectively regulated [9].

Below are additional details about various forms of magnesium.

Magnesium Oxide

This is the most common form of magnesium on the market. Although it is widely available in drug stores, relatively low-priced, and does not cause any harm, magnesium oxide doesn’t work well in humans because the body absorbs very little of it [2]. If a supplement simply lists “magnesium” as an ingredient without further explanation, it is probably magnesium oxide.

Magnesium Sulfate and Magnesium Chloride

Magnesium sulfate, aka Epson salt, is generally considered to be ineffective as a supplement. However, people do sometimes put it in bath water, where it can be absorbed through the skin [2].  Oil containing magnesium chloride can also be applied to the skin. Although little research has been done on whether magnesium oil has health benefits, one study found that it can reduce the pain of fibromyalgia [13].

Magnesium Citrate

Magnesium citrate has relatively high bioavailability and is fairly inexpensive, making it a better choice than magnesium oxide or magnesium sulfate. Magnesium citrate can also help prevent constipation and kidney stones [3, 7, 8]. It does cause upset stomach in some people.

Magnesium Glycinate and Magnesium Gluconate

If you are concerned about gastrointestinal side effects such as diarrhea, consider taking magnesium glycinate or magnesium gluconate. These forms of magnesium are less likely than other forms to cause such problems, and both of them have good bioavailability [5, 7]. In particular, magnesium glycinate is sold in a chelated form, meaning it has an extra amino acid that stabilizes it and helps prevent gastrointestinal side effects.

Water Solubility & Vitamin Interactions

According to some studies, the body absorbs water-soluble forms of magnesium (e.g. magnesium lactate, magnesium chloride, and magnesium citrate) better than those that are not water-soluble (magnesium oxide) [4].  

Multivitamins with magnesium usually contain magnesium oxide, although higher-quality multivitamins might contain magnesium citrate. The latter is better absorbed, but the amount of magnesium citrate in a  multivitamin is usually quite low because magnesium takes up a lot of space, and increasing the dosage would require very large pills. Also watch out for multivitamins that contain zinc, which reduces the intestines’ ability to absorb magnesium. By contrast, a B-vitamin complex or a multivitamin that contains vitamin B6 can increase absorption [1].

Which is the Best Magnesium Supplement?

Check out our unbiased recommendation of the best products on the market using our rigorous methodology. We screen products for the right formulation, bioavailability, safety, and efficacy to bring you only the best supplements available in 2019.

1. “Magnesium.” University of Maryland Medical Center. August 2015.
2. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. “Magnesium bioavailability from magnesium citrate and magnesium oxide.” J Am Coll Nutr. 1990 Feb;9(1):48-55.
3. Jahnen-Dechent, W., Ketteler, M. “Magnesium Basics.” Clinical Kidney Journal 5, 3-14 (2012).
4. Seelig, Mildred S. “The Requirement of Magnesium by the Normal Adult.” The American Journal of Clinical Medicine. Vol. 14. 6 (June 1964).
9. “Information for Consumers on Using Dietary Supplements.” U.S. Food and Drug Administration. September 2015.
10. Walker, Ann F.; Georgios Marakis; Samantha Christie; and Martyn Byng. “Mg citrate found more bioavailable than other Mg preparations in a randomized, double-blind study.” Magnesium Research. Vol. 16.3 (Sept. 2003):183-91.
11. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride.” Washington, DC: The National Academies Press, 1997, 190-240. Available at:
12. Riley, P. Thomas. “Magnesium.” University of Mary Washington Student Health Center. July 2011.