21st Century Magnesium Review

Magnesium is an essential mineral and supports bone and muscle health. For over 30 years, 21ST Century Vitamins has provided trusted vitamins and supplements by upholding the highest standards of quality in every product we offer. From sourcing the finest ingredients to rigorous testing and production processes, we ensure that every product meets our stringent quality benchmarks. We are here to support your wellness every step of the way. Directions: As a mineral supplement, adults take one (1) tablet daily with any meal or as directed by a healthcare provider. Do not exceed recommended dosage. Individual results may vary. Warning: Consult a healthcare provider prior to use if pregnant, nursing, on medications, have a medical condition, including kidney disease, or are planning a medical procedure. Stop use and contact a physician if adverse reactions occur. Keep out of reach of children. Do not use if product appears to be tampered with or seal is broken. Store at room temperature. Supplement Facts: Serving Size 1 Tablet. Elemental Magnesium (as Magnesium Oxide) 250 mg, 60% Daily Value. Calcium (as Calcium Carbonate) 65 mg, 5% Daily Value. No added Sugar, Yeast, Preservatives, Artificial Flavors or Colors. Dietary restrictions: Gluten Free, Non-GMO, Vegetarian, Vegan. Product is offered in 110 Tablets and 250 Tablets sizes.

Product Focus: Thyroid HealthAlso covers:HormonesMuscles and jointsDigestionBrain
Tier ⓘ
Members see this product's tier and why. Tiers run from 1, the strongest evidence, to 5. How we grade →
Evidence ⓘ
How strongly the evidence says this product works: human studies count most, then real reviews, then our biohacker panel.
Positive Reviews
Biohacker Mentions
Cost per month
$2

Study, Trial or Testing Result Summary

MembersHuman studies

Magnesium is at a studied dose of 250 mg, but thyroid evidence tested it with zinc and vitamin A. A review of 35 trials in 3,508 people with an underactive thyroid found that adding zinc, magnesium and vitamin A to meds free thyroxine, but magnesium was tested alone. …

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Review Totals and Summary

Members128,306 reviews
128,306 reviews · IHerb 73,961 · 21stcenturyvitamins 26,595 · Healthwarehouse 26,595 · EBay 1,146 · Walmart 9

"21st Century Magnesium" has garnered attention, with approximately 73961 ratings across various stores. Overall, customers generally find these magnesium tablets to be an affordable and effective supplement, though some exist regarding its form and absorption. ** Reported** users experience from taking these magnesium tablets. …

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Biohacker Summary

MembersWhat our biohacker panel says

of the panel or uses magnesium, and sleep is the main reason, with other reasons including blood pressure, stress, muscle recovery, and brain function. Forms they favor are glycinate and threonate, and doses mentioned include 400 mg of threonate before bed (taken by three of them), 300 mg before bed, and general targets of 400 to 600 mg a day. …

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RAL Summary

MembersThe tier and why

More Details

MembersBody systems · Combine with · Possible side effects

Body systems: Endocrine system, Musculoskeletal system, Digestive system, Nervous system. Combine with and possible side are for members.

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Supplement Facts

Calcium 65 mg · Magnesium 250 mg
Supplement Facts
Serving Size 1 Tablet
Amount Per Serving% Daily Value
Calcium (as Calcium Carbonate)65 mg5%
Magnesium (as Magnesium Oxide)250 mg60%

Other ingredients: Cellulose, Stearic Acid, Croscarmellose Sodium, Kelp. Contains <2% of: Gum Acacia, Magnesium Silicate, Magnesium Stearate, Silicon Dioxide.

Directions: Directions: As a mineral supplement, adults take one (1) tablet daily with any meal or as directed by a healthcare provider. Do not exceed recommended dosage. Individual results may vary.

Label source: 21stcenturyvitamins · Report a label change

Where to Buy

21st Century · iHerb · Healthwarehouse
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Our articles on this subject

Graded October 28, 2026 by the Reverse Age Lab evidence engine, from human studies, real reviews and our biohacker panel. How we grade. Is this medical advice? No. Rala organizes the published evidence; go over any change with your doctor, especially if you take meds.