Best magnesium supplements: NSF-certified picks by form and dose

We ranked by third-party testing, then form, then dose.

Third-party testing. Every product appears on NSF's certified supplement listing (NSF/ANSI Standard 173), checked November 3, 2026.

Form. We used the NIH Office of Dietary Supplements' own ranking, because it is the federal summary and it is short: forms that dissolve well in liquid absorb more completely, and the aspartate, citrate, lactate and chloride forms tend to be more bioavailable than magnesium oxide and sulfate. NIH says nothing about glycinate, bisglycinate or threonate, so we place them in a middle tier, ahead of oxide and behind the forms NIH names. That middle placement is our judgment, not NIH's.

Dose. The elemental magnesium in the serving NSF lists should be at or under 350 mg, the tolerable upper limit for adults for magnesium from supplements and medicines. Food magnesium does not count toward it. A product whose NSF-listed serving exceeds it is shown but not ranked. Products tied within a tier are listed alphabetically.

A product also needed a current NIH label record that matched its NSF row. One match is by brand, flavor and serving size rather than exact name: Garden of Life's NSF row reads "Garden of Life Magnesium Raspberry" (1 teaspoon, 4.9 g), and the NIH record reads "Whole Food Magnesium Raspberry Lemon" (1 teaspoon, 4.9 g).

No product on this page pays us, and none of the product links below is an affiliate link. Each row links to two public records instead: the product's row on NSF's certified supplement listing, and its label in the National Institutes of Health (NIH) Dietary Supplement Label Database. How to read both yourself is in how to check whether a supplement is third-party tested.

Certified, but we could not read a current label. Two citrate products are on NSF's listing: Thorne Magnesium CitraMate and up&up Highly Absorbable Magnesium Citrate 250 mg. Every Thorne CitraMate label in the NIH database is marked off the market, and we found no NIH record for the up&up citrate. Without a label record we could not verify the dose or other ingredients, so neither is ranked. If you prefer citrate, both are NSF-listed; read the panel on the bottle.

The up&up oxide label in the NIH database was entered in March 2013, the oldest record in this table. The formula may have changed since; check the bottle.

USP Verified: not checked. USP runs a separate verification program. Its public lookup refused our automated requests on November 3, 2026, so we did not check any product against it. "Not checked" in the table means we did not look. It does not mean a product failed.

NIH states that the Supplement Facts panel declares elemental magnesium, not the weight of the whole compound. The front of the bottle is not held to that. Double Wood sells "Magnesium Glycinate 400 mg", and its label record shows 60 mg of magnesium per capsule from 400 mg of magnesium glycinate. Momentous lists 2 g of magnesium L-threonate per serving and 144 mg of magnesium.

The difference is chemistry. By our calculation from the molecular formulas, magnesium oxide is about 60% magnesium by weight, citrate about 12 to 16% depending on the hydrate, and bisglycinate about 14%. So for the same milligrams of magnesium, glycinate or threonate products need far more powder or more capsules. Our glycinate vs citrate vs oxide guide reads the absorption studies behind each form.

Less than the marketing suggests. NIH reports that 48% of Americans take in less magnesium from food than their estimated requirement, an intake figure rather than a measured deficiency. The trial evidence for sleep, leg cramps, migraine and blood sugar is thin or negative; our guide does magnesium help you sleep? reads each one. The 2023 joint guideline from the American Gastroenterological Association and the American College of Gastroenterology made a conditional recommendation for magnesium oxide for chronic constipation, which is one of oxide's real uses.

If you take it at night for sleep, the timing question is answered in the best time to take magnesium.

High doses from supplements cause diarrhea, nausea and cramping, per NIH, and the forms most often reported to cause diarrhea are carbonate, chloride, gluconate and oxide. Very high doses can cause magnesium toxicity, with low blood pressure and irregular heartbeat. The kidneys remove excess magnesium, so people with reduced kidney function should ask a clinician before supplementing.

NIH's spacing rules: take magnesium at least 2 hours before or after an oral bisphosphonate such as alendronate; take tetracycline or quinolone antibiotics at least 2 hours before or 4 to 6 hours after a magnesium supplement. Long-term proton pump inhibitors and loop or thiazide diuretics can lower magnesium, which is a reason to ask for a level check rather than to self-dose.