**Magnesium** at 250mg per tablet lands within the clinical supplemental range of 100–400mg — but the form is magnesium oxide, which has roughly 4% absorption. That means your body is likely taking in only about 10mg of usable magnesium from each serving, well below what you'd need for meaningful support with sleep, stress, or muscle recovery.

The tablet also includes 65mg of **Calcium** as calcium carbonate, but that's a fraction of the 200–600mg supplemental range and won't move the needle for bone support. There are no complementary nutrients like vitamin D or K2 to enhance absorption of either mineral.

If you're supplementing magnesium for a specific health goal, the oxide form is the biggest limitation here. You'd absorb substantially more from a glycinate, citrate, or threonate form at the same dose — and those forms are also gentler on the stomach.

BioStacks
21st Century

Magnesium 250 mg

1 Tablet · 110 servings

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What it does

A combination of 2 label ingredients.

Magnesium

magnesium oxideBudget

magnesium oxide: Supports normal muscle function; small studies found oxide less well absorbed than citrate, with possible laxative effects.

Calcium

calcium carbonateBudget

Supports the maintenance of normal bones and teeth, muscle function and nerve signaling.

Heart
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Ingredients (2)

Calcium

65 mg

Trace amount — not scored

Other ingredients

KelpFood

Dried brown seaweed used as a whole-food source of iodine and trace minerals.

Microcrystalline CelluloseBinder

Plant-derived cellulose used as a binder and filler in supplements

Croscarmellose SodiumDisintegrant

Cross-linked cellulose derivative used as a superdisintegrant

Stearic AcidLubricant

Saturated fatty acid used as tablet lubricant

Lab testing

How to take it

With or without food
Space it a couple of hours from Iron and Calcium

On the label

Directions: As a mineral supplement, adults take one (1) tablet daily with any meal or as directed by a healthcare provider.

Price check

$4.99

$10$20$50

Cheaper than 99% of 579 magnesium supplements

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Sources & Scoring

Nutrient data (RDA, UL, and safety thresholds) sourced from the NIH Office of Dietary Supplements and the National Academies Dietary Reference Intakes (DRI).

This is not medical advice. Consult a healthcare provider before making changes to your supplement routine.

The score analyzes what's on the label: ingredient doses vs. studied ranges, chemical forms, evidence levels, and known interactions. It does not verify label accuracy or test for contaminants — for that, look for third-party certifications like USP or NSF.

Not medical advice. Consult your healthcare professional.

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