Magnesium L-Threonate: Benefits, Dosage and What the Research Shows

What is magnesium L-threonate?

It’s a magnesium salt of L-threonic acid, a breakdown product of vitamin C. It was developed by researchers at MIT, who found it raised brain magnesium in rats more than other forms. That is where its “brain magnesium” reputation comes from. Almost all of it is sold as Magtein.

Threonate is a large molecule, so little of each gram is magnesium. The European Food Safety Authority worked out that 3,000mg of magnesium L-threonate provides about 250mg of magnesium, and a 2026 trial gave 2g to deliver 145mg. That’s roughly 7 to 8%.

Not to be confused with L-theanine, an amino acid found in tea, or L-threonine, an essential amino acid. Our guide to L-theanine covers that one.

If you want everyday magnesium rather than threonate specifically, our Magnesium Glycinate Sleep Complex contains no threonate. It uses magnesium bisglycinate and citrate, giving 290mg of magnesium per serving, with glycine, L-theanine, chamomile, passionflower, hops and oat straw. Magnesium contributes to a reduction of tiredness and fatigue, to normal psychological function and to normal muscle function.

The FSA’s 10mg a day figure for CBD is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.

Magnesium L-threonate benefits: the evidence at a glance

There are only a handful of human trials, all small and short. Here is what each area rests on.

Who paid for the research? Every main trial of threonate on its own was funded or run with a company that makes or sells it. In the 2024 sleep trial, three of the six authors list AIDP, the ingredient’s distributor, as their affiliation. None of the trials compared threonate head to head with a cheaper form.

What a product can claim: there is no authorised health claim specific to threonate. Only the general magnesium claims apply, the same as for every form, for example: magnesium contributes to normal functioning of the nervous system, magnesium contributes to normal psychological function and magnesium contributes to a reduction of tiredness and fatigue.

Magnesium L-threonate for brain health and memory

The idea behind threonate is brain delivery. In the 2010 MIT study, rats given it had higher magnesium in the fluid around the brain and did better on learning and memory tests than rats given other forms. In people, nobody has measured brain magnesium after taking it; the trials measured test scores instead.

• Older adults (Liu, 2016): 44 people aged 50 to 70 with memory complaints scored better than placebo on an overall cognitive score after 12 weeks.
• Younger adults (Lopresti, 2025): 100 people aged 18 to 45 had better overall cognition, especially working and episodic memory, and faster reaction times after 6 weeks. There was no difference on a reasoning test.
• Combination formula (Zhang, 2022): 109 adults taking threonate with phosphatidylserine and vitamins C and D scored better on memory tests after 30 days, more so the older participants. Because it was a blend, it doesn’t tell you about threonate alone.

iTreat these as early signals, not proof. If concentration is your concern, many everyday factors play a part; see brain fog, magnesium and focus and our best supplements for focus. If it’s affecting daily life, speak to your GP.

Magnesium threonate for sleep: what the trials found

• Hausenblas, 2024: 80 adults with self-reported sleep problems took 1g a day, 2 hours before bed, for 3 weeks. Ring-tracked deep and REM sleep scores, and questionnaire scores for mood, energy and alertness, were better than placebo. The threonate group stayed steady while the placebo group declined.
• Lopresti, 2025: the larger trial found no difference in ring-tracked sleep. One self-reported measure (sleep-related impairment) improved; others didn’t.
• Mastrofini, 2026: an evening blend of 2g threonate, L-theanine and apigenin showed no clear benefit over placebo after 2 weeks.

So the sleep evidence is thinner than the marketing suggests, and the newest trials point both ways. Magnesium research on sleep in general, across all forms, is covered in magnesium for sleep. If sleep is your main reason for buying, glycinate gives far more magnesium per gram and is gentle on the stomach.

Magnesium threonate and anxiety

No trial has tested magnesium L-threonate for anxiety as its main aim. The 2016 trial measured anxiety, but the placebo group improved so strongly that the researchers couldn’t judge any effect. In the 2025 trial, general wellbeing scores didn’t differ from placebo. So there’s no good basis for calling threonate an anxiety supplement.

iFor what research shows on magnesium and anxiety more broadly, see magnesium for anxiety. If anxiety is affecting your daily life, speak to your GP.

Magnesium L-threonate dosage: how much, when and how long

Trials used 1 to 2g of magnesium L-threonate a day. The number on the front of the tub is usually the whole compound, so work out the elemental magnesium:

Capsule strengths vary, so reaching a trial dose usually means 2 to 4 capsules a day. Always follow the label.

• When to take it: the 2024 sleep trial gave the whole dose 2 hours before bed. The 2025 trial split it, 1g in the morning and 1g in the evening. Take it with food if it upsets your stomach; taking it every day matters more than the exact time. See best time to take magnesium.
• How long it takes: the trials measured changes after 3 to 12 weeks, and none showed an effect from a single dose. Give it at least 3 to 6 weeks before judging it. More in how long magnesium takes to work.
• Adding it up: the NHS says adults need 300mg (men) or 270mg (women) of magnesium a day, mostly from food, and that 400mg or less a day from supplements is unlikely to cause harm. If you take threonate with glycinate or a multivitamin, add up the elemental magnesium from each.

Magnesium L-threonate side effects and safety

• Common side effects: it was well tolerated in trials. In the 2025 trial of 100 adults, side effects were about as common as on placebo: 2 of the 50 people on threonate reported headaches and 2 reported looser stools. Each dose carries little magnesium, but high doses of any magnesium (over 400mg) can cause diarrhoea, as the NHS notes. See magnesium side effects.
• Kidney problems: speak to your GP first, because magnesium can build up.
• Medicines: magnesium can affect how some medicines are absorbed, including some antibiotics and bisphosphonates for osteoporosis such as alendronic acid. Ask your pharmacist about timing.
• Pregnancy and breastfeeding: the GB authorisation excludes pregnant and breastfeeding women, and we don’t recommend our products during pregnancy or breastfeeding either. See magnesium in pregnancy and speak to your midwife or GP.
• Children: no. In Great Britain it is authorised for adults 18 and over only, and there’s no good research in children. Speak to a GP before giving a child any magnesium supplement.

Is magnesium L-threonate legal in the UK?

Yes, since March 2026. It is a novel food, so it needed authorisation before it could be sold. The Food Standards Agency’s register lists it as authorised in England, Scotland and Wales (reference NOVEL-166) from 5 March 2026, after the European Food Safety Authority judged it safe in 2024. The conditions:

• food supplements only, for adults 18 and over, not pregnant or breastfeeding women
• no more than 250mg of magnesium a day from this ingredient
• labels must call it “Magnesium L-threonate” and say it shouldn’t be taken by under-18s or by pregnant or breastfeeding women
• the authorisation is held by AIDP Inc. and is data-protected for five years

Claims such as “brain magnesium”, “improves memory” or “boosts cognition” are not authorised health claims in the UK.

Magnesium threonate vs glycinate

The short version: threonate has the brain-focused research but the least magnesium per gram; glycinate gives about twice as much magnesium per gram, is gentle on the stomach and usually costs less per mg. They have never been tested head to head in people.

• Choose threonate if you specifically want the form used in the memory trials and accept the cost and the early evidence.
• Choose glycinate for an everyday, well-tolerated top-up, especially in the evening. See magnesium glycinate.
• Taking both is fine, as long as the total from supplements stays at 400mg a day or less.

Our full side-by-side guide, magnesium glycinate vs citrate vs threonate, covers absorption, cost and which suits which goal, and types of magnesium covers the other forms.

Is magnesium threonate worth the cost? Price per mg of magnesium

Compare products on the magnesium you actually get, not the size of the tub. Here is how much of each compound you swallow for 100mg of magnesium:

Figures are our approximate calculations, so always use the elemental magnesium on the label. To compare any two products, use this sum: price divided by (servings in the pot multiplied by mg of magnesium per serving), multiplied by 100, gives the cost per 100mg of magnesium.

Threonate usually works out the most expensive per mg, because you need about twice as much powder for the same magnesium and the GB authorisation is held by a single company. It is only worth that premium if the brain research is your reason for buying. For an everyday top-up, a cheaper form gives you more magnesium for your money.

How to choose a magnesium L-threonate supplement (UK)

1. Check the elemental magnesium per daily serving, not just the compound weight.
2. Check the UK label. It should name “Magnesium L-threonate” and carry the under-18s, pregnancy and breastfeeding warning. A product without these may not meet GB rules.
3. Look for Magtein if you want the ingredient used in the trials.
4. Count the capsules. Trial doses often mean 2 to 4 a day, which changes how long a tub lasts.
5. Be wary of brain claims and of “proprietary blends” that don’t say how much of each form is inside.
6. Buy from a UK seller who lists the full ingredients and can show test results.

Related guides

• For brands across all forms, see our guide to the best magnesium supplement in the UK.
• How much elemental magnesium per day you need, and why threonate capsules contain so little.
• For another form with big claims and little human research, see magnesium taurate benefits and evidence.
• Solgar also sells a threonate capsule; see our Solgar magnesium guide.
• Not sure whether to buy a powder or capsules? Read is magnesium powder better than tablets?
• Magtein is often marketed as a nootropic: see what UK rules allow in our nootropics UK guide.
• To see how much magnesium a threonate capsule really gives, read our Cytoplan magnesium page: 2,000mg of the compound gives 144mg of magnesium.