Magnesium L-threonate (mineral salt)

Magnesium L-threonate

Magnesium L-threonate was judged safe for adults at up to 3 g a day by the EU food safety authority, but the evidence that it sharpens memory or improves sleep is limited: two small trials funded by companies selling it found modest gains on combined memory and thinking scores, and in the main sleep trial the primary insomnia score improved no more than on placebo.

The claim that it gets magnesium into the brain comes from rat studies; we found no human study that measured brain magnesium. A 2 g daily dose gives only about 145 mg of magnesium, and people with kidney disease should ask a doctor first, because magnesium can build up.

Written by

Healthy and Herbal editorial team

Reviewed by

Healthy and Herbal editors

Updated

10 October 2026

White capsules on a desk beside an open notebook

At a glance

Last reviewed 10 October 2026

Evidence

Limited

Best for

Memory and thinking

Typical form & use

L-threonate 1.5–2 g (110–145 mg Mg)

Onset

4+ weeks

Safety

Kidney disease: magnesium can build up, ask first. No interactions in our data.

Check with your medications →

What it's used for

Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.

Use	Evidence	What the research shows
Memory and thinkingCompare remedies for focus and concentration →	Limited	In 44 adults aged 50–70 with memory complaints, anxiety and poor sleep, 1.5–2 g a day for 12 weeks improved a composite of four cognitive tests versus placebo (p = 0.003), although the trial had been sized around an anxiety score that did not change. In 100 adults aged 18–45 with poor sleep, 2 g a day for 6 weeks gave a marginal gain on the NIH Toolbox total cognition score (p = 0.043) and no difference on a reasoning test. Both trials were funded by companies selling the ingredient; an independently funded 12-week trial in 109 breast cancer survivors taking 1.2 g a day found no difference on a cognitive screening test. A 2026 review described the 12-week trial as short and small.^1,2,4,9
Poor sleep / insomnia symptomsCompare remedies for sleep →	Limited	In 80 adults aged 35–55 with self-reported sleep problems, 1 g a day for 3 weeks did not improve the primary Insomnia Severity Index more than placebo (p = 0.39); some secondary questionnaire items and Oura ring sleep-stage scores favoured it, but total sleep time and time to fall asleep did not differ. Sleep questionnaires showed no difference from placebo in the older-adult cognition trial or the breast cancer trial, and only one of two sleep scales did in the 6-week cognition trial.^3,1,4,2
Topping up magnesium	Limited	The European Food Safety Authority judged magnesium from this salt bioavailable, based on a dissolution test, two rat studies and one human trial. In that trial, red blood cell magnesium rose 3.3% over 12 weeks on 1.5–2 g a day while it fell slightly on placebo. The salt is only 7.2–8.3% magnesium, so each gram supplies roughly 75 mg.^5,1

Use

Evidence

What the research shows

Memory and thinkingCompare remedies for focus and concentration →

Limited

In 44 adults aged 50–70 with memory complaints, anxiety and poor sleep, 1.5–2 g a day for 12 weeks improved a composite of four cognitive tests versus placebo (p = 0.003), although the trial had been sized around an anxiety score that did not change. In 100 adults aged 18–45 with poor sleep, 2 g a day for 6 weeks gave a marginal gain on the NIH Toolbox total cognition score (p = 0.043) and no difference on a reasoning test.

Both trials were funded by companies selling the ingredient; an independently funded 12-week trial in 109 breast cancer survivors taking 1.2 g a day found no difference on a cognitive screening test. A 2026 review described the 12-week trial as short and small.^1,2,4,9

Poor sleep / insomnia symptomsCompare remedies for sleep →

Limited

In 80 adults aged 35–55 with self-reported sleep problems, 1 g a day for 3 weeks did not improve the primary Insomnia Severity Index more than placebo (p = 0.39); some secondary questionnaire items and Oura ring sleep-stage scores favoured it, but total sleep time and time to fall asleep did not differ.

Sleep questionnaires showed no difference from placebo in the older-adult cognition trial or the breast cancer trial, and only one of two sleep scales did in the 6-week cognition trial.^3,1,4,2

Topping up magnesium

Limited

The European Food Safety Authority judged magnesium from this salt bioavailable, based on a dissolution test, two rat studies and one human trial. In that trial, red blood cell magnesium rose 3.3% over 12 weeks on 1.5–2 g a day while it fell slightly on placebo. The salt is only 7.2–8.3% magnesium, so each gram supplies roughly 75 mg.^5,1

How much

Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.

Studied range (memory)

1.5–2 g compound daily (about 110–145 mg Mg)^1,2,3

The 12-week trial dosed about 25 mg per kg of body weight: 1.5 g for people of 50–70 kg and 2 g for 70–100 kg. The 6-week trial used 2 g a day, which it states provides 145 mg of magnesium. The 110 mg figure is our estimate from the sleep trial's 75 mg of magnesium per gram.

Studied range (sleep)

1 g compound daily (about 75 mg Mg)³

The sleep trial used two 500 mg capsules taken 2 hours before bed for 3 weeks; the authors put this at about 75 mg of magnesium.

Upper limit (EU)

250 mg supplemental Mg per day^6,5

The EU Scientific Committee on Food set this from mild diarrhoea appearing at about 360–365 mg; it excludes magnesium in food, and L-threonate is not among the salts it names. EFSA's 2024 assessment notes that 3 g of magnesium L-threonate, the maximum daily amount approved for adults, supplies about 250 mg of magnesium, the same as this limit.

Upper limit (US)

350 mg supplemental Mg per day⁷

Set by the US Institute of Medicine in 1997 with diarrhoea as the limiting effect; a 2023 review argues it is too conservative, but it remains the published figure.

Timing · The sleep trial took the whole 1 g dose 2 hours before bed; the 6-week cognition trial split 2 g into a capsule in the morning and one in the evening. No trial compared timings.With food? · The 6-week cognition trial allowed it with or without food, and the other trials do not say. One review of the upper-limit evidence suggests splitting magnesium doses through the day and taking them with food to reduce diarrhoea; this was not tested with L-threonate.How long to trial · The memory trials judged effects at 6 and 12 weeks, so allow at least 6 weeks. If nothing has changed by 12 weeks, it is unlikely to help you.

How people take it

Capsule (magnesium L-threonate alone)1–2 g compound (75–145 mg Mg)The form used in the trials, which tested one branded ingredient. Labels may quote the compound weight or the magnesium weight, so check which.

Combination productsVariesOften sold with phosphatidylserine or vitamins. A 30-day trial of one such blend (with phosphatidylserine and vitamins C and D) reported better memory test scores, but any effect cannot be pinned on the magnesium L-threonate.

Safety

Who should avoid

Kidney disease — magnesium can build up (hypermagnesaemia)
Pregnancy and breastfeeding — the EU safety assessment excluded these groups
Children — the EU safety assessment covered adults only
On regular medicines — check with a pharmacist first

Known interactions

No interactions in our data. Absence of a flag is not clearance.

Compare with

Head-to-head pages for the pairs people search most.

Magnesium L-threonate vs Magnesium glycinate

Questions people ask

Does magnesium L-threonate cross the blood-brain barrier?

In rats, yes: adding it to drinking water raised magnesium in the fluid around the brain. We found no human study that measured brain magnesium after taking it; the authors of the 2025 trial describe the evidence for raised brain magnesium as coming from animal and lab studies.

Does magnesium L-threonate improve memory?

Possibly, modestly, but it is not established. Two small trials funded by the companies selling it found gains on combined test scores after 6 to 12 weeks, one of them only just statistically significant.

An independently funded trial at a lower dose found no difference on a cognitive screening test. The 'years younger brain age' figures in these papers are estimates calculated from test scores, not measurements.

Is magnesium L-threonate good for sleep?

The evidence is weak. In the main sleep trial, the primary insomnia score improved just as much on placebo, although some secondary measures favoured magnesium L-threonate. Two other trials found no difference from placebo on sleep questionnaires.

How much magnesium is in magnesium L-threonate?

Not much: the salt is about 7.2–8.3% magnesium, so 2 g gives about 145 mg. EFSA's maximum of 3 g a day for adults supplies about 250 mg, the EU upper limit for supplemental magnesium.

Sources (9)

Reader notes

Experiences and questions from readers, read by an editor before they appear. They are personal accounts, not evidence, and are not medical advice.

Last reviewed 10 October 2026 · Next review April 2027 · How we rate evidence

Magnesium L-threonate

At a glance

What it's used for

How much

How people take it

Safety

Who should avoid

Known interactions

Compare with

Questions people ask

Does magnesium L-threonate cross the blood-brain barrier?

Does magnesium L-threonate improve memory?

Is magnesium L-threonate good for sleep?

How much magnesium is in magnesium L-threonate?

Sources (9)

Reader notes

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