Magnesium L-Threonate: Amounts Used in Research
Magnesium L-threonate is the form sold on a cognitive claim rather than a bowel-tolerance claim. The marketing rests largely on rodent work and one small human trial, and the compound weight on the label bears very little relation to how much magnesium you are actually taking.
Magnesium L-threonate is roughly 8% elemental magnesium, so the 2,000 mg (2 g) daily compound amount used in the MMFS-01 human trial supplies only about 144 mg of elemental magnesium — comfortably below the 350 mg adult upper intake level for supplemental magnesium set by the NIH Office of Dietary Supplements. Retail products typically supply 1,000–2,000 mg of the compound per serving, often split with part of the dose taken in the evening, mirroring the trial. The human evidence is one small randomised trial in older adults with cognitive complaints; it is not enough to establish a benefit.
Magnesium L-threonate amounts used in research and sold at retail
| Use case | Amount reported in sources | What to know |
|---|---|---|
| MMFS-01 randomised trial | About 1,500–2,000 mg compound per day (~25 mg/kg) | Twelve-week trial in adults aged 50–70 with cognitive complaints; dose was weight-adjusted and split. Source |
| Elemental magnesium in that amount | About 144 mg per day | The compound is roughly 8% magnesium by weight. Source |
| Upper limit for supplemental magnesium | 350 mg elemental per day | Applies to all supplemental magnesium forms combined, not to food. Source |
| Adult daily requirement (all sources) | 400–420 mg (men) / 310–320 mg (women) | Threonate alone does not cover the requirement at typical serving sizes. Source |
Figures are amounts reported in the cited sources, not a personal recommendation. Your own amount depends on your health, medicines and blood work.
The 8% problem: this form supplies very little magnesium
Every magnesium salt is a package: a magnesium ion attached to a carrier. In L-threonate the carrier is heavy relative to the mineral, so about 92% of what you swallow is threonic acid rather than magnesium. A 2,000 mg serving supplies roughly 144 mg of elemental magnesium — less than a single glycinate or citrate capsule in many cases.
That matters in two directions. If you are taking threonate to correct a low magnesium intake, it is an expensive and inefficient way to do it. If you are taking it for the cognitive claim and also taking another magnesium product, count the elemental totals together against the 350 mg supplemental limit.
It also explains the tolerability: because so little magnesium reaches the colon, threonate rarely causes the loose stools that limit citrate and oxide.
- Magnesium L-threonate: about 8% elemental magnesium.
- 2,000 mg of compound ≈ 144 mg of magnesium.
- Count that figure against the 350 mg supplemental upper limit.
What the human trial actually tested
The human evidence rests principally on MMFS-01, a twelve-week randomised, double-blind, placebo-controlled trial in adults aged 50–70 with self-reported cognitive complaints, sleep problems and anxiety. Participants received a weight-adjusted dose of magnesium L-threonate, split during the day with a portion in the evening.
The published results reported improvement on a composite cognitive measure relative to placebo. The caveats are substantial: a small sample, a single site, a composite primary outcome, and authors with commercial ties to the compound. Independent replication in a larger population has not followed at the scale the marketing implies.
The animal work behind it — showing raised cerebrospinal fluid magnesium and increased synaptic density in rodents — is the origin of the 'crosses the blood–brain barrier' claim. That mechanism has not been demonstrated to produce meaningful cognitive change in humans beyond this one trial.
Sleep, anxiety and the honest summary
Threonate is widely sold for sleep. Magnesium generally has modest and inconsistent evidence in insomnia, mostly in older adults and often in people whose intake was low to begin with. There is no trial establishing that threonate specifically outperforms cheaper forms for sleep.
If a magnesium supplement helps your sleep, the most likely explanation is that you were not getting enough magnesium — in which case glycinate or citrate at an equivalent elemental dose is the cheaper route to the same place.
The reasonable position is that threonate is well tolerated, delivers little magnesium per capsule, and has one small supportive human trial for cognition. Anything stated more strongly than that is ahead of the evidence.
Safety, kidneys and stacking
Reported adverse effects are mild — headache, drowsiness and occasional gastrointestinal upset. Because the elemental load is small, diarrhoea is uncommon compared with other forms.
The usual magnesium cautions still apply. People with reduced kidney function clear magnesium poorly and should not supplement without medical advice, and magnesium in any form reduces absorption of tetracycline and quinolone antibiotics and bisphosphonates when taken at the same time.
What the published studies found
Each entry below links straight to the paper or the health authority page so you can read the original rather than take our word for it.
- 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.
Twelve-week randomised, double-blind, placebo-controlled trial in adults aged 50–70
A weight-adjusted daily dose of magnesium L-threonate improved a composite cognitive measure relative to placebo in a small sample. The trial was industry-linked and has not been replicated at scale.
- Office of Dietary Supplements, National Institutes of Health. Magnesium — Fact Sheet for Health Professionals.
Health-authority reference document
Publishes the adult requirement, the 350 mg supplemental upper intake level, kidney-related cautions and documented drug interactions that apply to every magnesium form.
Side effects reported in the literature
Commonly reported
- Headache
- Daytime drowsiness when taken in larger evening doses
- Mild nausea
Serious, seek medical advice
- Hypermagnesaemia in people with reduced kidney function
- Reduced absorption of tetracycline and quinolone antibiotics taken at the same time
Summarized from NIH Office of Dietary Supplements magnesium fact sheet. Report anything unexpected to your own doctor or pharmacist.
Interactions to check with a pharmacist
| Medicine or condition | What sources report |
|---|---|
| Tetracycline and quinolone antibiotics | Magnesium binds the antibiotic in the gut, reducing absorption; separate the doses. Source |
| Bisphosphonates | Absorption of the bisphosphonate falls when taken with magnesium. Source |
| Other magnesium supplements | Elemental amounts add together against the 350 mg supplemental upper limit. Source |
This is not a complete interaction list. Check your own medicines with a pharmacist before combining anything.
This page is reference material, not medical advice. Supplements interact with prescription medicines and with each other. Talk to a doctor or pharmacist before starting anything, especially if you are pregnant, breastfeeding, managing a health condition or taking prescription medicine.
Frequently asked questions
How much magnesium L-threonate should I take?
The human trial used a weight-adjusted amount of roughly 25 mg of compound per kilogram, which worked out at about 1,500–2,000 mg a day split across the day. That supplies only around 144 mg of elemental magnesium.
How much elemental magnesium is in magnesium L-threonate?
About 8% by weight. A 2,000 mg serving of the compound gives roughly 144 mg of magnesium, which is why the label figure looks large next to other forms.
Does magnesium L-threonate actually improve memory?
One small twelve-week randomised trial in older adults with cognitive complaints reported improvement on a composite measure. It was industry-linked and has not been independently replicated at scale, so the claim is promising rather than established.
Is magnesium L-threonate better than glycinate?
For raising magnesium intake, no — glycinate and citrate deliver far more elemental magnesium per capsule. Threonate's distinct claim is cognitive, and that rests on a single small human trial.
Should I take it at night?
The trial split the dose with a portion in the evening, and most retail products follow that pattern. There is no evidence that a different schedule would work worse.
Can I take it with other magnesium supplements?
You can, but add up the elemental magnesium across everything you take and keep the supplemental total at or below 350 mg a day unless a clinician has advised otherwise.
Keep reading
Sources
- Liu G, et al. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults. J Alzheimers Dis. 2016;49(4):971–990.
- Office of Dietary Supplements, National Institutes of Health. Magnesium — Fact Sheet for Health Professionals.
- MedlinePlus, U.S. National Library of Medicine. Magnesium in diet.
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