How to Choose a Magnesium Supplement
Magnesium supplements come in many forms, and they behave quite differently. Here is how to tell them apart.
Last reviewed: October 2026 · How we research
Disclosure: As an Amazon Associate I earn from qualifying purchases. This guide is general information, not medical advice. Talk to your doctor before starting any supplement.
The common forms
- Magnesium citrate: Widely sold and absorbed reasonably well. It can loosen stools, especially at higher amounts.
- Magnesium glycinate (bisglycinate): Often chosen because it tends to be gentle on the stomach. It usually costs more.
- Magnesium oxide: Inexpensive and packed with magnesium per pill, but not absorbed as well, and more likely to cause loose stools.
- Malate, threonate and others: Often marketed for specific purposes. The evidence for special benefits is limited, so avoid paying extra just for the name.
Read the label
- Elemental magnesium. The Supplement Facts panel should show the amount of actual magnesium, not just the weight of the compound. This is the number to compare.
- Serving size. Many products need two or more capsules to reach the listed dose.
- Upper limit. The NIH Office of Dietary Supplements lists 350 mg a day from supplements and medications as the upper limit for adults, and going above it can cause diarrhea, nausea and cramping. Stay within the label directions.
- Third-party testing. Look for seals from USP, NSF or similar independent labs.
Practical tips
- If a supplement upsets your stomach, take it with food or try a gentler form.
- Food sources include nuts, seeds, leafy greens, beans and whole grains. Many people get a good share from diet.
- If you have kidney problems or take medications such as certain antibiotics, osteoporosis drugs or diuretics, ask your doctor or pharmacist first, since magnesium can interact with them.
Sources and further reading
We read these pages in October 2026. They come from government health agencies in the United States and are not affiliated with this site. Where official advice differs between countries, we say so in the guide. Always follow the advice of your own doctor or pharmacist.
- NIH Office of Dietary Supplements: Magnesium, consumer fact sheet (page dated March 2021)
- NIH Office of Dietary Supplements: Dietary Supplements, What You Need to Know (page dated January 2023)
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