Guide

Magnesium forms: match the form to the goal

Q: Which magnesium is best for sleep?

Bisglycinate has the only randomized sleep trial with a positive primary endpoint: 155 adults, 4 weeks, Insomnia Severity Index 1.6 points better than placebo, p=0.049, Cohen's d=0.20, at 250 mg/day elemental. The effect is real and small.

Q: What is the difference between compound and elemental magnesium?

Compound weight is the whole salt. Elemental is the magnesium atom inside it. A label reading 2,200 mg magnesium glycinate carries about 310 mg elemental magnesium, a 7.1-fold gap. The Supplement Facts panel declares elemental. Front-of-bottle copy often does not.

Q: Can I take too much magnesium?

Yes. The EC Scientific Committee on Food set a tolerable upper intake level of 250 mg/day of supplemental elemental magnesium. Mild diarrhea appeared around 360 to 365 mg/day. Toxic hypermagnesaemia was reported only above 2,500 mg/day oral. Kidney impairment lowers the safe ceiling.

Q: Does magnesium taurate work?

No human trial of magnesium taurate was located. The blood pressure evidence is 30 rats given 2 to 4 mg/kg/day for 4 weeks. PubChem does not publish a molecular weight for the compound, so the elemental percentage cannot even be computed from a cited source.

There are 8 supplemental magnesium forms. Each is best for a different endpoint. Choosing the wrong form is why most people do not feel their magnesium.

8 supplemental formsSCF UL 250 mg/day elemental7.1x compound-to-elemental gap typical3 forms with real endpoint evidence

The label trick: compound weight is not magnesium

2,200 mg magnesium glycinate = 310 mg magnesium

2,200 mg → 310 mg

Magnesium glycinate has a molecular weight of 172.42 g/mol and magnesium weighs 24.305 u, so 14.1% of the compound is magnesium[17]. The number on the front of the bottle is 7.1 times the number that matters. The Supplement Facts panel is required to declare elemental magnesium, not the weight of the whole compound[1].

Form	Compound weight on a common label	Elemental %	Elemental mg delivered
Magnesium oxide	400 mg	60.30%	241 mg
Magnesium chloride	500 mg	25.53%	128 mg
Magnesium sulfate	500 mg	20.19%	101 mg
Magnesium citrate	1,000 mg	16.16%	162 mg
Magnesium malate	1,000 mg	15.54%	155 mg
Magnesium glycinate	2,200 mg	14.10%	310 mg
Magnesium L-threonate	2,000 mg	8.25%	165 mg
Magnesium taurate	not stated	n.a.	n.a.

Percentages are arithmetic from PubChem molecular weights and the magnesium atomic weight of 24.305 u. Taurate has no molecular weight published on its PubChem record, so its elemental share cannot be computed from a cited source.

Elemental density and absorption run in opposite directions. Oxide is 60.30% magnesium and absorbs at roughly 4%[7]. Citrate is 16.16% magnesium and produced the highest serum and salivary levels in a 46-person, 60-day randomized comparison, while oxide showed no difference from placebo[6]. Solubility explains it: citrate is about 55% soluble in plain water, oxide is close to insoluble[15].

Match the form to the goal

Eight forms, each with the strongest human evidence attached to it. Open the form you are considering.

Magnesium glycinate (bisglycinate)14.1% elemental

Best evidence: sleep. A 155-person randomized trial over 4 weeks moved the Insomnia Severity Index by 1.6 points more than placebo, p=0.049, Cohen's d=0.20, at 250 mg/day elemental[2] Second endpoint: pregnancy leg cramps, where 86.0% versus 60.5% of women reached a 50% cramp reduction, p=0.007, number needed to treat 3.9[3]

What it is for: sleep and cramps at a dose you can tolerate, plus general repletion if the pill count does not bother you.

What it is not for: a dramatic sleep fix. The effect is 1.6 ISI points. It is also not a high-density form: 14.1% means a 2,200 mg capsule stack carries 310 mg elemental[17] One 40-person crossover found no significant plasma rise after bisglycinate at all[1]

Magnesium L-threonate (Magtein)8.25% elemental

Best evidence: cognition. A 100-person, 6-week trial in adults aged 18 to 45 with poor sleep found the NIH Total Cognition Composite favored threonate, p=0.043, reaction time p=0.031[4] A separate 80-person, 21-day trial measured sleep outcomes[18]

What it is for: cognition. It is the only form with a positive cognition trial as its primary endpoint.

What it is not for: raising magnesium status. At 8.25% elemental, a 2 g compound dose carries about 165 mg elemental magnesium. Fluid intelligence was null in the same trial, p=0.953[4] It is also the most expensive magnesium per elemental milligram on the market.

Magnesium citrate16.16% elemental

Best evidence: migraine prevention. 600 mg/day for 12 weeks cut attack frequency 41.6% versus 15.8% on placebo, p<0.05[5] Citrate also produced the highest serum and salivary magnesium of the forms tested over 60 days[6] and ranks high on absorption in older comparisons[7]

What it is for: migraine prophylaxis and efficiently raising blood magnesium.

What it is not for: a calm stomach. The migraine trial reported 18.6% diarrhea and 4.7% gastric irritation at 600 mg/day[5]

Magnesium malate15.54% elemental

Best evidence: none that survives blinding. The only randomized study is a 24-person fibromyalgia crossover, and its blinded fixed-dose phase found no clear treatment effect. Pain reductions appeared only in the open-label dose-escalation phase[8]

What it is for: nothing proven. It is a reasonable general-repletion salt if you already own it.

What it is not for: energy or fibromyalgia, despite the marketing. There is no human trial supporting an energy claim for malate.

Magnesium tauratenot computable from a cited molecular weight

Best evidence: 30 rats. Magnesium taurate at 2 and 4 mg/kg/day for 4 weeks against cadmium-induced hypertension in Sprague Dawley rats[9] No human trial of magnesium taurate was located.

What it is for: nothing that human data support today.

What it is not for: blood pressure. Magnesium in general lowers systolic pressure by about 2 mm Hg across pooled trials, and the form used was usually not stated[1] That pooled effect is not evidence for taurate specifically.

Magnesium oxide60.30% elemental, the highest of the eight

Best evidence: constipation. 1,500 mg/day compound for 28 days produced 70.6% overall improvement versus 25.0% on placebo, p=0.015, with colonic transit time p<0.001[10]

What it is for: constipation, and nothing else.

What it is not for: correcting magnesium status. Fractional absorption is about 4%[7] and 300 mg/day for 60 days produced no difference from placebo on magnesium markers[6] Oxide is close to insoluble in water[15] The highest elemental percentage on the shelf is attached to the worst absorption.

Magnesium chloride25.53% elemental

Best evidence: depression. 248 mg/day elemental for 6 weeks improved PHQ-9 by a net 6.0 points adjusted, 95% CI 7.9 to 4.2, p<0.001, with effects visible within 2 weeks[11] Secondary endpoint: insulin resistance, HOMA-IR 3.8 versus 5.0, p=0.005, over 16 weeks[12]

What it is for: cheap repletion, low mood as an adjunct, and insulin sensitivity signals. Absorption is in the same tier as citrate[7]

What it is not for: a substitute for depression treatment. It was tested alongside usual care, not against it.

Magnesium sulfate20.19% elemental, anhydrous basis

Best evidence: intravenous, not oral. The 10,141-woman Magpie trial cut eclampsia from 1.9% to 0.8%, a 58% relative reduction[13] That is a hospital drug protocol.

What it is for: clinical obstetric use, and bath salts.

What it is not for: daily oral supplementation. No oral longevity indication exists, and the European upper-level opinion singles sulfate out for the extra osmotic load[14]

What to avoid

Taurate. No human trial exists. The whole blood pressure story rests on 30 rats[9]. Price it accordingly.

Malate sold for energy. The blinded phase of the only randomized study reported no clear treatment effect[8]. The energy claim comes from the malic acid half of the name, not from a trial.

Oxide sold for anything except constipation. It has the constipation trial[10] and it has 4% fractional absorption[7]. Using it to correct magnesium status means swallowing the laxative effect for almost none of the mineral.

Mixed-form sleep formulas. Blends that list four salts and a total compound weight usually deliver a sub-therapeutic elemental dose. The sleep trial used 250 mg/day elemental from 1,786 mg of compound[2]. If a sleep blend cannot show you an elemental figure in that range, it is not running the studied protocol.

Split what you do take. Relative uptake is higher across several small doses than one large one[16].

Safety and interactions

The EC Scientific Committee on Food set the tolerable upper intake level for supplemental magnesium at 250 mg/day elemental, with an uncertainty factor of 1.0. The no-observed-adverse-effect level was 250 mg/day and mild diarrhea appeared at roughly 360 to 365 mg/day. Toxic hypermagnesaemia was reported only above 2,500 mg/day oral[14]. Several of the trials above run above the ceiling on purpose: 300 mg for cramps, 600 mg for migraine, 1,500 mg of oxide compound for constipation.

Kidney impairment. Reduced kidney function clears magnesium poorly and raises the risk of hypermagnesaemia. Anyone with chronic kidney disease should not self-dose magnesium[1].

Drugs that deplete magnesium. Loop and thiazide diuretics increase renal magnesium loss. Proton pump inhibitors taken for a year or more have been associated with hypomagnesaemia[1].

Drugs magnesium binds. Magnesium forms complexes with fluoroquinolone and tetracycline antibiotics and with oral bisphosphonates, cutting their absorption. Separate the doses by at least 2 hours[1].

Diarrhea is the dose-limiting side effect for every form. At 600 mg/day of citrate it hit 18.6% of participants[5].

How our top-rated magnesium products stack up

Ranked by our six-pillar overall score. Form and endpoint fit are read from the product label data we hold. No brand pays for placement.

Magnesium Bisglycinate

Thorne HealthTech

Glycinate
200 mg magnesium per serving
Endpoint fit: sleep and cramps

Score 8.6/10

Nitralis®

DoNotAge

Form not stated in label data
800 mg magnesium per serving
Endpoint fit: general repletion

Score 8.5/10

Magnesium Glycinate Powder

BulkSupplements

Glycinate
310 mg magnesium per serving
Endpoint fit: sleep and cramps

Score 8.2/10

Pure Vitamin D3, K2 & Magnesium

DoNotAge

Form not stated in label data
250 mg magnesium per serving
Endpoint fit: general repletion

Score 8.2/10

Basic Nutrients 2/Day

Thorne HealthTech

Form not stated in label data
20 mg magnesium per serving
Endpoint fit: general repletion

Score 7.9/10

Two-Per-Day Multivitamin (capsules/tablets)

Life Extension

Form not stated in label data
100 mg magnesium per serving
Endpoint fit: general repletion

Score 7.7/10

See the full ranking: Best Magnesium Supplements 2026.

Frequently asked questions

Which magnesium is best for sleep?

Bisglycinate has the only randomized sleep trial with a positive primary endpoint: 155 adults, 4 weeks, Insomnia Severity Index 1.6 points better than placebo, p=0.049, Cohen's d=0.20, at 250 mg/day elemental. The effect is real and small.

Is magnesium threonate worth the price?

It is the only form with a positive cognition trial as its primary endpoint: 100 adults, 6 weeks, NIH Total Cognition Composite p=0.043. It is also the weakest form by elemental content at 8.25%, so it is a poor choice for correcting magnesium status. Buy it for cognition or not at all.

What is the difference between compound and elemental magnesium?