Magnesium L-Threonate
This is a form of magnesium studied for brain effects. The rat study it's based on didn't compare it with other magnesium forms, human research is still early, and all three human trials so far have company ties (see the research section).
Magnesium L-threonate is a magnesium compound studied for brain effects. A 2010 rat study found it raised brain magnesium and improved memory measures compared with an unsupplemented diet; it didn't compare it with other magnesium forms. The human trials so far are small and mostly industry-funded.
Research & evidence
Strong support Some support Weak or no supportColours show how well the sources back each point. The reason is next to each one.
In a 2010 animal study (Slutsky et al., Neuron), magnesium L-threonate (MgT) supplementation increased brain magnesium and improved learning and memory measures in rats compared to an unsupplemented control diet. This study did not test MgT head-to-head against other magnesium forms. The paper discloses that its senior author was a cofounder of Magceutics, a company developing drugs for age-related memory decline.
Preclinical onlyWeak or no support. Mostly lab or animal studies
Study details
Slutsky et al. 2010 compared MgT-treated rats with rats on a normal diet; it did not test MgT against other magnesium salts (oxide, citrate, etc.). The only mention of other forms in the paper is a reference to a separate 1984 study, not a comparison arm in this experiment. The paper's Acknowledgments state that senior author Guosong Liu "is a cofounder of Magceutics, a company whose goal is to develop drugs to treat age-dependent memory decline and Alzheimer's disease." The same author led the main human trial in the next claim.
Source: Slutsky I, Abumaria N, Wu LJ, et al. "Enhancement of learning and memory by elevating brain magnesium." Neuron. 2010 Jan 28;65(2):165-177. View source
Small human trials suggest magnesium L-threonate may improve sleep quality and some measures of cognitive function. Only one of these trials specifically studied older adults with memory complaints (n=44, ages 50-70); the other two studied younger or middle-aged adults with sleep complaints, not memory issues. All three trials have limitations: two were directly funded by companies with a commercial stake in the ingredient (one of which initially omitted this from its published disclosure and had to issue a correction), and the newest trial used a statistical threshold (one-tailed testing) that makes several of its "significant" findings weaker than they'd appear under standard methods.
Limited evidenceSome support. Based on one or a few small trials
Study details
Liu et al. 2016 (n=44, ages 50-70, cognitive complaints; the only one of these trials in older adults with memory complaints): overall cognitive ability improved vs. placebo (p=0.003, Cohen's d=0.91); same senior author (Guosong Liu) as the animal study above. Hausenblas et al. 2024 (n=80, ages 35-55, sleep complaints, not memory-focused): subjective sleep improvements, but a June 2025 Corrigendum states the initial competing-interest disclosure was incomplete: "AIDP Inc. commissioned and funded this study, and owns patents"; 3 of 6 authors are AIDP employees/consultants, and the trial was not registered on clinicaltrials.gov in a timely manner. Lopresti & Smith 2026 (n=100, ages 18-45, sleep complaints, not older adults): primary cognition outcome significant (p=0.043), but about 20 other measured outcomes were not significant, including every objective Oura-ring sleep metric and most individual cognitive subtests; funded by Threotech Inc., which also holds the study's IP and was "involved in the conceptualisation of the study design"; it used one-tailed significance testing throughout, so several reported "significant" p-values (0.043, 0.041, 0.033) would not clear a standard two-tailed 0.05 threshold.
Source: 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." J Alzheimers Dis. 2016;49(4):971-990; Hausenblas HA, Lynch T, Hooper S, et al. "Magnesium-L-threonate improves sleep quality and daytime functioning." Sleep Med X. 2024;8:100121 (see Corrigendum, Sleep Med X. 2025;9:100141); Lopresti AL, Smith SJ. "The effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality." Front Nutr. 2026 Jan 12;12:1729164. View source
Dosage
| Form | Amount |
|---|---|
| Any form | There's no recommended dose for magnesium L-threonate specifically. The recommended daily amount of magnesium from all sources is 400–420 mg for men and 310–320 mg for women. The upper limit for magnesium from supplements is 350 mg a day for adults. |
Side effects
Well documented Reported (case reports, anecdotal or one study) None reportedThe circle shows how well documented an effect is, not how serious it is. A rarely reported effect can still be serious, so always read ‘When to stop’.
| Effect | Frequency | When to stop |
|---|---|---|
| Diarrhea, nausea, stomach cramps (magnesium supplements in general)Well documentedListed plainly by NIH, MSK or LiverTox | Often, with high doses | Stop and talk to a doctor if it persists. |
Safety & interactions
Safety
Neither NIH nor MSK has safety information specific to magnesium L-threonate. For magnesium supplements in general, NIH says high doses often cause diarrhea, which can come with nausea and stomach cramps. The upper limit for magnesium from supplements is 350 mg a day for adults, and the risk of magnesium toxicity rises with poor kidney function.
Contraindications
MSK says not to take magnesium supplements if you have kidney problems such as renal insufficiency or end-stage renal disease, gastrointestinal problems such as a bowel obstruction, or heart block, and that people with heart, kidney or gastrointestinal disorders shouldn't take them without a doctor's supervision. MSK also says not to take magnesium if you take sulfonylurea diabetes drugs, because it may cause low blood sugar. These cautions are for magnesium in general; MSK doesn't cover the L-threonate form.
Drug interactions
Shares magnesium's chelation interaction with other forms: forms complexes with tetracycline and quinolone antibiotics, reducing their absorption. Take the antibiotic at least 2 hours before, or 4 to 6 hours after, a magnesium-containing supplement. The sources describe magnesium in general; they don't cover the L-threonate form specifically. (The nitrofurantoin interaction comes from a single source.)
Shares magnesium's absorption-reducing interaction with oral bisphosphonates. Separate doses by at least 2 hours in either direction. The sources describe magnesium in general; they don't cover the L-threonate form specifically.
Shares the interaction documented for magnesium generally: IV magnesium sulfate given during surgery is well documented to potentiate neuromuscular blocking agents — shortening onset time and prolonging their effect (anesthesiologists sometimes use this intentionally as an adjuvant). Whether an oral magnesium supplement (including this form) has a similar effect hasn't been directly studied — the evidence base, including Memorial Sloan Kettering's own cited sources, covers only IV magnesium given in clinical/surgical settings. As a precaution, tell your surgeon or anesthesiologist if you take magnesium supplements. This does not describe oral muscle relaxants such as cyclobenzaprine or baclofen.
Shares the interaction described for magnesium generally: magnesium-containing products could have an additive effect on blood pressure when combined with calcium channel blockers (MSK's own hedge). MSK's only reference for this is a review of high blood pressure in pregnancy. The sources describe magnesium in general; they don't cover the L-threonate form specifically.
These diuretics increase magnesium loss in urine and can lead to magnesium depletion with long-term use — applies to magnesium from any form, including L-threonate.
Potassium-sparing diuretics reduce magnesium excretion, which can raise magnesium levels — the opposite effect from loop and thiazide diuretics. Applies regardless of magnesium form.
Long-term prescription PPI use (typically more than a year) can cause low blood magnesium (hypomagnesemia). The FDA advises checking serum magnesium before starting long-term PPI treatment and periodically during use. Applies regardless of which magnesium form is used to correct it.
Magnesium supplements or antacids can increase how fast and how much sulfonylurea drugs are absorbed (MSK, citing a 1994 review of antacid drug interactions). MSK's patient guidance says not to take magnesium with them, because it may cause low blood sugar. MSK describes magnesium in general, not the L-threonate form.
Established: stated plainly by an authoritative source. Documented: supported by case reports or trial data. Theoretical: based on mechanism, animal data, or a cautious listing. Always check with your pharmacist or prescriber.