Magnesium Glycinate: What It Is, How Much to Take, and How It Compares

Magnesium glycinate (also sold as magnesium bisglycinate) is magnesium bound to two molecules of the amino acid glycine. It is about 14% elemental magnesium by weight, is not among the forms NIH lists as most likely to cause diarrhea, and was the form tested in a 2025 placebo-controlled sleep trial. Adults should keep supplemental magnesium at or below 350 mg a day unless a clinician advises more.

Magnesium Glycinate vs Citrate, Oxide, Malate, Threonate and Taurate

*Calculated by FormulaCompare from the anhydrous molecular formula of each salt (magnesium atomic weight 24.305). Commercial ingredients may be hydrated or buffered with other salts, which changes the real figure, so always read the elemental amount on the Supplement Facts panel — NIH ODS notes labels must declare elemental magnesium, not the weight of the whole compound. Absorption statements: NIH ODS magnesium fact sheet.

What is magnesium glycinate?

Magnesium glycinate is a chelate: one magnesium ion held by two glycine molecules. Glycine is a non-essential amino acid that your body also makes. Because glycine is small and the compound dissolves readily, manufacturers describe it as gentle on the stomach. The practical facts that matter are simpler: it carries roughly 14 mg of magnesium per 100 mg of compound, so a capsule labeled “magnesium glycinate 1,000 mg” delivers about 140 mg of actual magnesium. If a label only gives the compound weight, it is hiding the number you need.

How much magnesium glycinate should you take?

The NIH Office of Dietary Supplements sets the adult Recommended Dietary Allowance at 400–420 mg/day for men and 310–320 mg/day for women (350–360 mg in pregnancy). That RDA counts food, water and supplements together. Separately, the Tolerable Upper Intake Level for supplemental magnesium is 350 mg/day for everyone aged 9 and older. Food magnesium does not count toward that 350 mg ceiling because the kidneys clear excess from food.

In practice, most glycinate products supply 100–200 mg of elemental magnesium per serving. The 2025 bisglycinate sleep trial used 250 mg/day elemental magnesium. Staying in the 100–350 mg range keeps you within the official limit. Higher doses, such as the 600 mg/day used in some migraine trials, should only be taken under medical supervision, as NIH ODS states.

Does magnesium glycinate help you sleep?

Modestly, and the best evidence is recent. In a 2025 randomized, double-blind trial of 155 adults with self-reported poor sleep, 250 mg/day elemental magnesium as bisglycinate reduced Insomnia Severity Index scores by 3.9 points at week 4 versus 2.3 points on placebo (p = 0.049). The authors called the effect small (Cohen’s d = 0.2) and noted larger improvements in people with low dietary magnesium intake (Schuster et al., Nat Sci Sleep 2025). So glycinate is a reasonable first try if your diet is low in nuts, seeds, beans and greens, but it is not a sedative.

Magnesium glycinate vs citrate: which is better?

Pick by what you want the magnesium to do. NIH ODS says small studies found citrate, aspartate, lactate and chloride more completely absorbed than oxide and sulfate. We could not find an NIH-cited trial showing glycinate absorbs better than citrate, so claims that glycinate is “the most absorbable form” are marketing. The real difference is in the gut: citrate pulls water into the bowel and is used as a laxative, while glycinate is chosen to avoid that. For constipation, citrate. For a daily top-up or bedtime use without a trip to the bathroom, glycinate.

Best magnesium form by goal

This is a form ranking, not a brand ranking. We do not take payment for placements.

• Best for sleep: glycinate — the only form with a 2025 placebo-controlled insomnia trial, and gentle on the gut.
• Best for constipation: citrate — well absorbed and reliably laxative at higher doses. See citrate vs MiraLAX.
• Best value per mg: oxide — about 60% magnesium by weight, but lower absorption and more diarrhea.
• Best for cognition claims: L-threonate — promising animal data, one small human trial, highest cost per mg.
• Skip unless you have a reason: malate and taurate — little form-specific human evidence.

Who actually needs a magnesium supplement?

NIH ODS reports that 48% of Americans get less magnesium from food than the Estimated Average Requirement, with men over 70 and teenagers most likely to fall short. Groups at higher risk include people with Crohn’s or celiac disease, type 2 diabetes, alcohol dependence, and older adults. Long-term proton pump inhibitor use (usually more than a year) and loop or thiazide diuretics can also lower magnesium. Early deficiency signs are vague: loss of appetite, nausea, fatigue and weakness. Serum tests are imperfect because less than 1% of body magnesium is in the blood.

Magnesium glycinate side effects and safety

The common side effect of any magnesium supplement is diarrhea, sometimes with nausea and cramps. NIH ODS lists carbonate, chloride, gluconate and oxide as the forms most often reported to cause it. Serious toxicity is rare and usually involves very large doses of laxatives or antacids (typically more than 5,000 mg/day) or kidney failure. Anyone with reduced kidney function should not supplement without medical advice, because the kidneys are how the body removes excess magnesium.

Magnesium glycinate interactions to know

NIH ODS lists three practical spacing rules. Take oral bisphosphonates such as alendronate at least 2 hours apart from magnesium. Take tetracycline or quinolone antibiotics (doxycycline, ciprofloxacin, levofloxacin) at least 2 hours before or 4–6 hours after magnesium. Long-term PPIs and some diuretics can drain magnesium, so ask your prescriber whether to test. For general timing advice see our supplement timing guide.

Magnesium glycinate vs food sources

Food is often enough. Per NIH ODS, an ounce of roasted pumpkin seeds provides 156 mg, an ounce of chia seeds 111 mg, an ounce of almonds 80 mg and half a cup of boiled spinach 78 mg. Roughly 30–40% of dietary magnesium is absorbed. If you eat those foods daily, a supplement adds little; if you rarely do, 100–200 mg of glycinate is a sensible gap-filler.

Magnesium Glycinate FAQ

Is magnesium glycinate the same as magnesium bisglycinate?

Yes. Bisglycinate means two glycine molecules are bound to each magnesium ion, which is the usual structure of magnesium glycinate. Labels use both names for the same ingredient.

How much elemental magnesium is in magnesium glycinate?

About 14% by weight for pure anhydrous magnesium glycinate, so 1,000 mg of the compound gives roughly 140 mg of magnesium. Buffered blends can differ, so read the elemental amount on the Supplement Facts panel.

What is the maximum safe dose of magnesium glycinate?

The NIH Tolerable Upper Intake Level for supplemental magnesium is 350 mg of elemental magnesium per day for adults. Magnesium from food does not count toward this limit. Higher doses should only be used under medical supervision.

Is magnesium glycinate good for sleep?

It may help a little. A 2025 randomized trial in 155 adults with poor sleep found 250 mg/day of magnesium as bisglycinate lowered insomnia scores slightly more than placebo after 4 weeks, with a small effect size.

Should I take magnesium glycinate in the morning or at night?

Timing matters less than taking it consistently. Many people take it in the evening because it is used for sleep and does not usually cause urgent bowel movements.

Is magnesium glycinate better than magnesium citrate?

Not for absorption, as far as published evidence shows. NIH ODS cites studies showing citrate absorbs better than oxide, but no trial showing glycinate beats citrate. Glycinate is gentler on the gut; citrate is better if you want a laxative effect.

Can magnesium glycinate cause diarrhea?

It can at high doses, like any magnesium, but it is less often linked to diarrhea than oxide, carbonate, chloride or gluconate, which NIH ODS names as the most common culprits.

Who should not take magnesium glycinate?

People with kidney disease should not take magnesium supplements without medical advice. People on bisphosphonates or tetracycline and quinolone antibiotics need to space doses apart from magnesium.

Does magnesium glycinate interact with medications?

Yes. Separate it from oral bisphosphonates by at least 2 hours, and take tetracycline or quinolone antibiotics at least 2 hours before or 4 to 6 hours after magnesium, according to NIH ODS.

Sources

1. NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated January 6, 2026)
2. Schuster J, et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025;17:2027-2040
3. Slutsky I, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010;65(2):165-77
4. Liu G, et al. Efficacy and safety of MMFS-01 (magnesium L-threonate) for cognitive impairment in older adults: an RCT. J Alzheimers Dis. 2016;49(4):971-90