Magnesium from trials and meta-analyses: blood pressure, sleep in older adults, the L-threonate memory trial, and monthly cost at the dose a review used.
Researched from published studies and manufacturer specifications, checked .
We have not tested products ourselves. How we research
Magnesium has moderate evidence for lowering blood pressure and low-quality evidence for shortening time to fall asleep in older adults. The L-threonate memory trial was a single 30-day study of a branded formula. Kidney disease and some medicines make magnesium unsafe to self-treat. Ask your doctor.
Talk to your doctor first. This is general information, not medical advice. Supplements and devices can interact with medicines and health conditions. We quote study protocols for context and do not recommend doses.
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Thorne · $26 for 90 servings (Thorne's site, 28 Sept 2026)
Price as of July 2026. Check the retailer for the current price and availability.
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The short answer: magnesium has moderate evidence for lowering blood pressure, and low-quality evidence that it shortens the time to fall asleep in older adults. The memory results for magnesium L-threonate come from one 30-day trial of a branded formula. If you have kidney disease or take certain medicines, magnesium can be unsafe to self-treat, so talk to your doctor first.
Grades follow the rubric.
| Question | Grade | Evidence | Limit |
|---|---|---|---|
| Blood pressure | Moderate | A meta-analysis of 34 RCTs (2,028 people): systolic -2.00 mm Hg (CI 0.43 to 3.58), diastolic -1.78 mm Hg; median dose 368 mg/day elemental magnesium for a median 3 months | Small change in a surrogate marker; residual heterogeneity per the authors; trials vary in form and population |
| Sleep onset in older adults | Weak | A meta-analysis of 3 RCTs (151 people): sleep onset 17.36 minutes shorter (CI -27.27 to -7.44); total sleep time not significant | All trials at moderate-to-high risk of bias; evidence quality low to very low |
| Memory (L-threonate) | Emerging | One RCT, 109 adults, Magtein PS 2 g/day for 30 days: better scores on all five memory subtests | Single 30-day trial of a branded formula containing phosphatidylserine and vitamins C and D, in healthy Chinese adults aged 18 to 65; the authors declare no competing interests |
Form matters for what you pay, not for proven outcome: no head-to-head trial in our search shows one form outperforming another.
The number on the front of a magnesium bottle is often the weight of the whole compound, not the magnesium in it. The trials count elemental magnesium, so the useful column is elemental milligrams. From our cost per study dose dataset: brand pages read 28 to 29 Sept 2026, USD, before tax, shipping and subscription discounts; the last two columns are our arithmetic.
| Product | Price | Elemental Mg per serving | Price per 100 mg elemental Mg | Per month at 368 mg/day | Testing stated |
|---|---|---|---|---|---|
| Nutricost Magnesium Glycinate Powder, 250 g (135 scoops) | $21.97 | 210 mg | $0.08 | $8.56 | generic “third-party tested” banner, no certifier |
| Thorne Magnesium Glycinate, 90 capsules | $26 | 120 mg (1 capsule) | $0.24 | $26.58 | none stated |
| Thorne Magnesium Bisglycinate powder (60 scoops) | $52 | 200 mg | $0.43 | $47.84 | NSF Certified for Sport (stated on page) |
| Momentous Magnesium L-Threonate, 30 servings | $49.99 | 145 mg, in 2 g of Magtein (3 capsules) | $1.15 | $126.87 | NSF Certified for Sport (stated on page) |
The 368 mg a day is the median dose across the blood pressure trials, not a target. Threonate is the priciest way to get magnesium; its case rests on the memory trial, which used a different formula: Magtein PS at 2 g a day, which also contains phosphatidylserine and vitamins, whereas Momentous lists Magtein alone at 2 g a serving. We found no trial of that exact product.
The NHS says adults aged 19 to 64 need 300 mg a day (men) or 270 mg (women) and that 400 mg or less a day from supplements is unlikely to cause harm; more can cause diarrhoea. Kidneys clear magnesium, so kidney disease raises the risk of accumulation. Magnesium can also interact with some antibiotics and other medicines; ask a pharmacist or your doctor before taking it. Diarrhoea is a common effect of higher supplement intakes. This page gives no personal dose.
See magnesium in the graded supplement ladder, pair it with the sleep hygiene protocol and sleep tools, and compare forms. Related: vitamin D3 + K2, the complete stack and the magnesium evidence card.
Only some brands name a certifier; what each certification checks.
Researched from PubMed abstract records, NHS and brand pages, checked 29 Sept 2026. Abstracts only; grades are our judgement using the published rubric. We did not test any product. General information, not medical advice.
See also: Glycine for sleep: the trials and the cost.
A 2021 meta-analysis of 3 randomised trials in 151 older adults found sleep onset 17.4 minutes shorter with magnesium than placebo, but the evidence quality was low to very low and all trials had moderate-to-high risk of bias. Total sleep time did not change significantly.
A meta-analysis of 34 randomised trials (Hypertension 2016; 2,028 participants) found magnesium supplementation lowered systolic pressure by 2.00 mm Hg and diastolic by 1.78 mm Hg. It is a marker, not a disease outcome, the authors note residual heterogeneity, and the median dose was 368 mg of elemental magnesium for a median of 3 months.
One 30-day RCT in 109 healthy Chinese adults found a magnesium L-threonate and phosphatidylserine formula (Magtein PS, 2 g/day) improved memory scores versus placebo. It is a single trial of a branded product; no trial we found compares forms head to head.
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