Verified Supplement Data Evidence-based supplement comparisons

Your Doctor Said Take Magnesium — Here's Exactly Which One to Buy

By Verified Supplement Data · Published · Methodology · About Us

Short answer: Get magnesium glycinate unless your doctor specified a different form. It's the best-absorbed common form and is gentle on the stomach.

Best value: Vitamin Shoppe Magnesium Glycinate 400mg — $0.24/day, full dose in 2 tablets.

If quality testing matters to you: Nature Made Magnesium Glycinate (USP Verified) — $0.47/day, independently tested for purity and potency.

The 3 Things You Need to Know

1. Get Glycinate, Not Oxide

The most common (and cheapest) magnesium on pharmacy shelves is magnesium oxide. It has very low bioavailability — your body only absorbs about 4% of it. Most passes through your system unused.

Magnesium glycinate is significantly better absorbed. It costs slightly more per bottle but much less per absorbed dose. It also won't cause the laxative effect that oxide and citrate can.

See our full comparison of all 8 magnesium forms

2. Check the "Elemental Magnesium" Amount

This is where most people get confused. Supplement labels can be misleading:

  • "Magnesium Glycinate 2,000mg" might only contain 280mg of actual magnesium
  • Look at the Supplement Facts panel for the line that says "Magnesium" with the form in parentheses
  • The number next to "Magnesium" is the elemental amount — that's what your body uses
  • Aim for your doctor's recommended dose in elemental magnesium

Full dosage guide with detailed label reading instructions

3. Take It With a Meal (or Before Bed)

  • With food improves absorption and reduces any chance of stomach upset
  • Before bed is ideal if your doctor recommended it for sleep, anxiety, or muscle cramps — the glycine component has calming effects
  • If taking 400mg+, consider splitting into two doses (morning and evening)

Our Recommendations

Best magnesium supplements — ranked by cost per day for a 400mg dose
Product Mg/Serving Cost/Day Certification Buy
BulkSupplements Magnesium Glycinate Powder 225 mg $0.18 None Buy on Amazon
Vitamin Shoppe Magnesium Glycinate 400mg 400 mg $0.24 None Buy on Amazon
Nature Made Magnesium Glycinate 200mg 200 mg $0.47 USP Verified Buy on Amazon
Doctor's Best High Absorption Magnesium 200 mg $0.51 None Buy on Amazon
KAL Magnesium Glycinate 400 400 mg $0.62 None Buy on Amazon
Thorne Magnesium Bisglycinate 200 mg $0.87 NSF Certified for Sport Buy on Amazon

Cost per day calculated for a 400mg elemental magnesium dose. Products with less than 400mg per serving require multiple servings, increasing daily cost. See full buying guide.

What Your Doctor Might Have Recommended It For

Doctors commonly recommend magnesium for:

  • General deficiency — blood work showed low levels, or you have risk factors. Learn about deficiency signs
  • Sleep — meta-analysis shows magnesium reduces time to fall asleep by 17 minutes. Sleep evidence review
  • Muscle cramps — especially nocturnal leg cramps. Leg cramp evidence
  • Anxiety — RCT evidence for mild-to-moderate anxiety. Anxiety evidence review
  • Migraine prevention — American Academy of Neurology Level B recommendation
  • Heart health — meta-analysis of 34 trials shows blood pressure reduction
  • Pregnancy — higher RDA during pregnancy (350-360mg/day)

Frequently Asked Questions

My doctor said to take magnesium — which kind should I buy?

Magnesium glycinate unless they specified otherwise. Best absorbed, gentlest on stomach. Vitamin Shoppe Glycinate 400mg is $0.24/day. Nature Made (USP Verified) is $0.47/day if quality testing matters.

What dose of magnesium should I take?

Follow your doctor's recommendation. If unspecified: 200-400mg elemental magnesium/day. Check the Supplement Facts label for the elemental amount. Full dosage guide.

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