Magnesium threonate
Sold as the magnesium that reaches the brain, for sleep and memory. The trials are small and company-funded, and it has never been compared with the cheaper form we use.
At a glance
| Our verdict | Small company-funded trials, three times the price of bisglycinate, never compared with it. |
| Sold for | Memory, sleep and ADHD (claimed) |
| How sure the evidence is | Low, company-funded |
| Cost a month | About $40 to $60 (estimated) |
Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.
Supplement Check
Is it right for you?
If magnesium suits you, the form and the dose matter, and so do your kidneys and the medicines you take. Your check works it out and tells you whether to switch. Our Supplement Check looks at:
- Kidney function below normal (eGFR under 60), or unknown when there is a kidney risk
- Heart block
- Myasthenia gravis
- Every medicine you take
- The total across everything you already take, against the safe upper limits
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
What it is
Magnesium L-threonate is magnesium bound to threonic acid, sold under the patented name Magtein. It is only about 7 to 8% magnesium: 2 g gives about 144 mg. Magnesium bisglycinate, the form we use, is about 14 to 20% magnesium.
How it acts
In rats it raised magnesium in the fluid around the brain. In people the evidence that it reaches the brain better is indirect. That is the basis of the marketing, not proof of a benefit.
What it is used for, and what the evidence says
| Use | What the trials found | How sure we are |
|---|---|---|
| Sleep and thinking, adults with poor sleep (6 weeks) | 100 adults took 2 g a day. A combined thinking-test score was better (only just past the line for chance) and so was self-rated sleep-related impairment, but sleep measured by a ring tracker did not change. Funded by the patent holder. [1] | Low |
| Sleep, adults aged 35 to 55 (3 weeks) | 80 adults took 1 g a day: better ring-measured deep and dream (REM) sleep scores and daytime mood. Run with the sponsor. [2] | Low |
| Older adults with memory problems (12 weeks) | 44 people: thinking scores improved by a large amount on paper, but the trial was small and run by the maker, and sleep could not be judged because the placebo group also improved. [3] | Low (maker-run) |
| ADHD | No trial of either form of magnesium in adult ADHD. People with ADHD have lower blood magnesium in observational studies, which does not show that taking magnesium helps. [4] | No evidence (no trial) |
| Against magnesium bisglycinate | Never compared head to head. | No evidence (no trial) |
How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.
Benefits
- Small, mostly self-reported gains in sleep in company-funded trials. [1, 2]
- No ADHD symptom data.
Risks and side effects
- Diarrhoea, less than with magnesium oxide.
- Too much magnesium in the blood when the kidneys do not work well.
Interactions with medicines
Magnesium binds some medicines in the gut, so they must be taken 2 to 4 hours apart. Our review found no report that it speeds up or blocks the liver enzymes that clear medicines; that question has not been studied for it.
| Medicine | What can happen | What to do |
|---|---|---|
| Quinolone and tetracycline antibiotics | Less antibiotic absorbed | Take 2 to 4 hours apart |
| Bisphosphonates (bone-strengthening medicines) | Less absorbed | Take 2 to 4 hours apart |
| Levothyroxine | Less absorbed | Take 2 to 4 hours apart |
| HIV integrase inhibitors | Less absorbed | Take 2 to 4 hours apart |
Who should not take it
- Kidney function below normal (eGFR under 60), or unknown when there is a kidney risk: a kidney blood test comes first, for any form of magnesium. That includes anyone on a medicine that can harm the kidneys or with a history that could cause kidney problems.
- Heart block.
- Myasthenia gravis.
- Under 18: outside the Supplement Check.
Dose and timing
We do not recommend a dose. For reference, trials used 1 to 2 g of magnesium threonate a day (about 70 to 144 mg of magnesium).
- Our magnesium is magnesium bisglycinate, 400 mg at night.
- Magnesium from any product counts toward your daily total.
- Dr. French's rule is one form only, magnesium bisglycinate. Anyone on another form is advised to switch; the other forms are more likely to loosen the bowels.
What we know about Canadians
Magnesium is the mineral Canadians most often fall short on from food. In the 2015 national nutrition survey, 58% of men and 66% of women ate less than the average requirement, and the shortfall grows with age. [5] Among adults 19 to 64 in households with enough food it was 49%; in households with severe food insecurity it was 76%. [6] There is no reliable blood test for body magnesium.
Most at risk: older adults, women, food-insecure households, diets low in whole grains, legumes and nuts, and people on water pills or long-term acid blockers. None of this says which form to take: a shortfall is met just as well by bisglycinate.
How sure are we: moderate. National survey, but based on two days of recalled food and 11 years old.
An honest comparison: sleep
Cost a month in Canadian dollars. The threonate trials measured self-rated sleep and tracker scores rather than minutes to fall asleep, so its row is described in words.
| Option | Effect | How sure we are | Cost a month (CAD) |
|---|---|---|---|
| Magnesium bisglycinate 200 to 400 mg | About 17 minutes faster to sleep in older adults [8] | Low to Very low | $15 to $20 |
| Magnesium threonate 1 to 2 g | Self-rated gains; no clear change on objective sleep measures [1, 2] | Low (low, company-funded) | $40 to $60 (estimated) |
| Cognitive behavioural therapy for insomnia (app, programme or therapist) | 19 minutes faster to sleep, 26 minutes less awake in the night; the effect lasts after treatment ends [7] | Moderate to High | Free (app) to about $90 (therapist) |
| Sleeping pill (zopiclone in Canada) | 22 minutes faster to sleep on sleep studies; the benefit stops when the pill stops [9] | Moderate | $8 to $12 |
Why we don't recommend it
We do not sell magnesium threonate. If magnesium suits you for sleep, our check recommends magnesium bisglycinate, alongside a sleep programme.
Already taking it? Switch to bisglycinate: it is about a third of the price, and Dr. French's rule is bisglycinate only. Have a kidney blood test first if you take a medicine that can harm the kidneys or have any kidney history.
The sleep and memory trials of magnesium threonate are small and funded by the company that holds the patent, and they showed self-reported gains rather than clear changes on objective sleep measures. [1, 2] It costs about three times as much as magnesium bisglycinate ($40 to $60 against $15 to $20 a month) and has never been compared with it. If magnesium suits you for sleep, bisglycinate is the form we use, alongside a sleep programme, which works better than either.
Supplement Check
Before you buy it, get it checked
If magnesium suits you, the form and the dose matter, and so do your kidneys and the medicines you take. Your check works it out and tells you whether to switch. Our Supplement Check looks at:
- Kidney function below normal (eGFR under 60), or unknown when there is a kidney risk
- Heart block
- Myasthenia gravis
- Every medicine you take
- The total across everything you already take, against the safe upper limits
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
Disclosure of financial interest
White Pine Medical earns money from products bought through our Fullscript dispensary. Dr. French's Code of Ethics requires him to tell you this. You do not have to buy anything from us: every product is named by its ingredient and dose so you can buy it at any pharmacy, and the advice is the same wherever you buy it, or if you buy nothing.
References
- Lopresti AL, Smith SJ. The effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Front Nutr. 2025;12:1729164. PMID 41601871.
- Hausenblas HA, Lynch T, Hooper S, et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Med X. 2024;8:100121. PMID 39252819.
- Liu G, Weinger JG, Lu ZL, Xue F, Sadeghpour S. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults: a randomized, double-blind, placebo-controlled trial. J Alzheimers Dis. 2016;49(4):971-90. PMID 26519439.
- Effatpanah M, Rezaei M, Effatpanah H, et al. Magnesium status and attention deficit hyperactivity disorder (ADHD): a meta-analysis. Psychiatry Res. 2019;274:228-34. PMID 30807974.
- Ahmed M, Praneet Ng A, L'Abbe MR. Nutrient intakes of Canadian adults: results from the Canadian Community Health Survey (CCHS)-2015 Public Use Microdata File. Am J Clin Nutr. 2021;114(3):1131-40. PMID 34020449.
- Hutchinson JM, Tarasuk V. Prevalence of micronutrient inadequacy differs by severity of food insecurity among adults living in Canada in 2015. Appl Physiol Nutr Metab. 2024;49(8):1025-34. PMID 38603809.
- Trauer JM, Qian MY, Doyle JS, Rajaratnam SM, Cunnington D. Cognitive behavioral therapy for chronic insomnia: a systematic review and meta-analysis. Ann Intern Med. 2015;163(3):191-204. PMID 26054060.
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complement Med Ther. 2021;21(1):125. PMID 33865376.
- Huedo-Medina TB, Kirsch I, Middlemass J, Klonizakis M, Siriwardena AN. Effectiveness of non-benzodiazepine hypnotics in treatment of adult insomnia: meta-analysis of data submitted to the Food and Drug Administration. BMJ. 2012;345:e8343. PMID 23248080.
Costs marked as estimates are typical Canadian retail or pharmacy prices, before any drug plan. Certainty grades are ours unless the review gave its own.