Magnesium L-Threonate
The magnesium form engineered to reach the brain. The animal data is striking; the human evidence is still early.
1.5-2 g/day magnesium L-threonate (~144 mg elemental)
C Mixed or limited evidenceNootropicsSleep
Vitamins & Minerals · Sleep
Magnesium (Glycinate & Citrate)
Also known as: magnesium bisglycinate, magnesium citrate, magnesium oxide, magnesium
An essential mineral that roughly half of adults under-consume, sold in forms that differ enormously in whether they are absorbed or just laxative.
Grade BGood human evidence
Studied dose200-400 mg elemental magnesium/day
TimingEvening suits most people, since the sl…
EvidenceGrade B
CategoryVitamins & Minerals
Essentiality and the consequences of deficiency are settled. Supplementation reliably corrects low status and modestly improves sleep, anxiety, and blood pressure — with the largest effects in people who were low to begin with.
Magnesium is unusual on this list in that the deficiency is real and widespread. Dietary surveys consistently put a large share of adults below the estimated average requirement, and the reasons are structural: refined grains lose most of their magnesium in milling, soil concentrations have declined, and the foods richest in it — nuts, legumes, leafy greens, whole grains — are exactly what modern diets skimp on. Blood tests hide this well, since serum magnesium is defended tightly at the expense of bone and muscle stores.
Where it helps is where you would predict from a cofactor that participates in every ATP reaction. Sleep improves modestly, particularly in older adults and those with low intake — falling asleep faster, waking less. Subjective anxiety and stress ratings improve in a reasonably consistent set of trials. Blood pressure drops a few mmHg. Migraine prophylaxis has enough support that neurology guidelines mention it. And it genuinely helps constipation, though that is the citrate form doing what osmotic laxatives do.
The form question is where most of the money is wasted. Magnesium oxide is the cheapest and fills the majority of drugstore products; it is around 4% bioavailable and its main reliable effect is a trip to the bathroom. Glycinate (bisglycinate) is well absorbed, gentle on the gut, and the glycine itself has mild sleep-promoting properties — the sensible default for evening use. Citrate is well absorbed and mildly laxative, which is a feature or a bug depending on your situation. L-threonate is the form marketed for cognition on the basis that it raises brain magnesium in rats; it has its own entry here and a considerably weaker human case.
Check the label for elemental magnesium, not compound weight — "500 mg magnesium glycinate" may contain only 50-70 mg of actual magnesium, which is the number that matters. Start at 200 mg, take it with food, and increase only if your gut tolerates it.
How it works
Magnesium is a required cofactor for over 300 enzymes, including every reaction that uses ATP. Relevant to the popular claims, it acts as a natural NMDA receptor antagonist and GABA agonist — a genuinely calming signature — and regulates vascular smooth muscle tone and neuromuscular excitability.
What the evidence supports
- Corrects low magnesium status straightforward nutrient repletionA
- Improves subjective sleep quality clearest in older adults and those with low intakeB
- Reduces subjective anxiety and stress consistent direction across small-to-moderate trialsB
- Lowers blood pressure a few mmHg, larger in hypertensive and deficient subjectsB
- Reduces migraine frequency enough support to appear in neurology guidance, at higher dosesC
Safety
Very safe from food and at supplemental doses in people with healthy kidneys — excess is simply excreted. The dose-limiting effect is diarrhoea, not toxicity. Kidney impairment changes this picture entirely: magnesium accumulates and can become dangerous, so anyone with reduced renal function needs medical advice first.
Reported side effects
- Loose stools or diarrhoea, especially with oxide and citrate
- Nausea or cramping at large single doses
Interactions
- Reduces absorption of tetracycline and quinolone antibiotics, and of bisphosphonates and levothyroxine — separate by at least 2-4 hours.
- Proton pump inhibitors used long-term lower magnesium levels.
- Caution with kidney disease: excretion is impaired and levels can rise.
This guide is educational, not medical advice. Talk to a physician or pharmacist before starting any supplement, especially alongside prescription medication or a medical condition.
Common questions
- What does Magnesium (Glycinate & Citrate) do?
- An essential mineral that roughly half of adults under-consume, sold in forms that differ enormously in whether they are absorbed or just laxative. Its best-supported effects are corrects low magnesium status and improves subjective sleep quality.
- Does Magnesium (Glycinate & Citrate) actually work?
- Good human evidence (grade B). Essentiality and the consequences of deficiency are settled. Supplementation reliably corrects low status and modestly improves sleep, anxiety, and blood pressure — with the largest effects in people who were low to begin with.
- How much Magnesium (Glycinate & Citrate) should I take?
- The studied range is 200-400 mg elemental magnesium/day, daily, often in the evening. Start at the low end — more is not better once the effective range is covered.
- When should I take Magnesium (Glycinate & Citrate)?
- Evening suits most people, since the sleep and relaxation effects are the ones you notice. Split doses above 300 mg to reduce laxative effect.
- Is Magnesium (Glycinate & Citrate) safe?
- Very safe from food and at supplemental doses in people with healthy kidneys — excess is simply excreted. The dose-limiting effect is diarrhoea, not toxicity. Kidney impairment changes this picture entirely: magnesium accumulates and can become dangerous, so anyone with reduced renal function needs medical advice first. The most reported side effects are loose stools or diarrhoea, especially with oxide and citrate, nausea or cramping at large single doses.
- What should you not mix Magnesium (Glycinate & Citrate) with?
- Reduces absorption of tetracycline and quinolone antibiotics, and of bisphosphonates and levothyroxine — separate by at least 2-4 hours. Proton pump inhibitors used long-term lower magnesium levels. Caution with kidney disease: excretion is impaired and levels can rise. Ask a pharmacist or physician before combining it with prescription medication.
References
Evidence review last updated