This magnesium delivers 400mg per softgel, but it's **magnesium oxide** — a form your body absorbs at only about 4%. So while 400mg sits at the top of the supplemental range on paper, in practice you're getting a small fraction of that.

Where oxide does work is the gut: the unabsorbed magnesium pulls water into your bowel, which is why it's mainly used for occasional constipation, and why the label warns of diarrhea and caps you at one softgel. That's a real effect, just not the one most people buy magnesium for.

If your goal is sleep, muscle relaxation, or correcting low magnesium, a glycinate or citrate form is far better absorbed. For that goal this falls short; for occasional constipation, it does the job.

BioStacks
Nature Made

High Potency Magnesium 400 mg

Capsule · 1 Softgel · 150 servings

iHerbAmazon

Best for

Heart

Ingredients (1)

Magnesium

100%

Dose

400 mg

Target

100–400 mg

Form

Budget

Nutrition

Calories, macros & sodium.

  • Calories10 Calorie(s)
    • Calories from Fat5 Calorie(s)
  • Total Fat0.5 Gram(s)

Other Ingredients (6)

Medium Chain Triglyceride OilCarrier

Fractionated oils rich in C8/C10 triglycerides used as neutral carrier or anti-sticking agent

Soy LecithinEmulsifier

Widely used emulsifier derived from soybeans

GelatinCapsule

Protein derived from collagen, used in traditional capsule shells

GlycerinHumectant

Sweet-tasting liquid used in soft capsules and liquids

Purified WaterSolvent

Water meeting USP specifications used as solvent/vehicle in gummies and liquids

BeeswaxCoating

Natural wax produced by honeybees, used as a coating and binding agent in softgels and tablets

How to Take It

Best taken in the evening

Magnesium oxide is poorly absorbed (~4%) and the most laxative form. Most of a dose stays in the gut, which is why it's mainly used for constipation — a poor pick if you're supplementing for magnesium itself.

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

On the label

Suggested use: Take one softgel daily, with a meal. For easier swallowing, take with water before and during ingestion.

General guidance based on the ingredients, not a substitute for the label or your doctor.

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Sources & Scoring

Nutrient data (RDA, UL, and safety thresholds) sourced from: NIH Office of Dietary Supplements and 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. clinical 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.

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