Klean Magnesium

The practical details.

Before you buy

Evidence & sources.

Do creatine, fish oil, vitamin D and magnesium work? Our evidence review grades the research as Mixed. That grade is about the claim, not about this product.

• CertificationNSF's Certified for Sport database lists two US entries named "Klean Magnesium" by Klean Athlete. Both are mineral and vegan capsules with a package size of 90 and a serving size of 1 capsule. One (listing 1281622) lists the flavor as unflavored and shows 11 certified lot numbers. The other (listing 1572352) lists the flavor as Other and shows 13. Two lot numbers appear in both, so 22 are different.^{3–5, 12} Checked in NSF's own database. Klean's product page shows no product-specific NSF mark or lot lookup (the NSF logo appears only in the site footer and menu), and its data sheet doesn't mention NSF. So the listings are the evidence of certification. Neither entry shows a certification date, the magnesium amount or a SKU. NSF doesn't say how the two relate. You can match the lot number on your bottle to the listed lots. NSF says it verifies that the label matches the contents. It also says products don't contain unsafe levels of contaminants, prohibited substances or masking agents.
• Manufacturer claimKlean's page says Klean Magnesium supports an athlete's energy production, muscle contraction and relaxation, and recovery time between workouts. Its data sheet says magnesium glycinate is a chelate that increases the bioavailability of magnesium. It cites studies and states their findings in general terms, without figures. The page carries the standard FDA disclaimer.^{1, 7} These are Klean's own statements for a dietary supplement. The page's disclaimer says the FDA hasn't evaluated them. It also says the products aren't intended to diagnose, treat, cure or prevent any disease. This review didn't assess them.
• Independent testNIH's Office of Dietary Supplements gives the Tolerable Upper Intake Level for supplemental magnesium as 350 mg for adults. That counts magnesium from supplements and medications, not food. High doses from these sources can cause diarrhea, nausea and abdominal cramping. The limit is 65 mg at ages 1 to 3 and 110 mg at ages 4 to 8. Toxicity risk rises with impaired kidney function. ODS lists interactions with oral bisphosphonates, tetracycline and quinolone antibiotics, loop and thiazide diuretics and long-term proton pump inhibitors.⁸ One 120 mg capsule is under the adult limit, with 230 mg to spare for any other supplement or medicine. Three capsules (360 mg) and four (480 mg) are above it. ODS says to take magnesium at least 2 hours before or after oral bisphosphonates. It says to take the antibiotics at least 2 hours before or 4 to 6 hours after magnesium. ODS also says absorption varies by form, and forms that dissolve well in liquid generally absorb better. It doesn't name glycinate.
• Independent testNIH's Office of Dietary Supplements describes magnesium as a cofactor in more than 300 enzyme systems. These include protein synthesis and muscle and nerve function. It says magnesium is required for energy production. It also says symptomatic magnesium deficiency is uncommon in healthy people.⁸ The fact sheet doesn't discuss exercise performance, recovery or muscle soreness, so it doesn't back or contradict Klean's claims about athletes. It's context on what the mineral does in the body, not a finding about this product.
• Regulator recordopenFDA's food enforcement reports returned no match for "Klean Athlete" in the product-description field on Oct 24, 2026. They also returned none for "Klean" or "Klean Athlete" in the recalling-firm field. A search of FDA's warning letters database for "Klean Athlete" returned no letters. FDA lists that content as current as of Oct 20, 2026.^{10, 11} These are name searches. They would miss a recall or letter filed under another name, such as a parent company or contract manufacturer. FDA's warning letters search may not cover older letters.