Minerals
Magnesium L-Threonate — timing, dose & interactions
Form designed to raise magnesium in the brain, which it did in rats. In an industry-sponsored randomized trial in adults with sleep complaints, it improved sleep-quality scores. It supplies little elemental magnesium per gram, so it's a poor way to correct a deficiency.
Also known as: Magtein, Magnesium threonate
Timing
When to take it
Commonly taken in the evening, sometimes split morning and evening.
Dose note. UL applies to all supplemental magnesium combined (not food); mainly to prevent diarrhea.
Interactions
Magnesium L-Threonate with other supplements
Magnesium L-Threonate + Calcium
Very high calcium may reduce magnesium absorption
Magnesium L-Threonate + Zinc
Very high zinc can reduce magnesium absorption
Magnesium L-Threonate + Vitamin D3
Magnesium is required to activate vitamin D
Magnesium L-Threonate + Psyllium Husk
Fiber can reduce magnesium absorption
Magnesium L-Threonate + Potassium
Low magnesium makes low potassium hard to fix
Magnesium L-Threonate + Magnesium
Two forms of magnesium
Magnesium L-Threonate + Magnesium Glycinate
Two forms of magnesium
Magnesium L-Threonate + Magnesium Citrate
Two forms of magnesium
Magnesium L-Threonate + Magnesium Malate
Two forms of magnesium
Magnesium L-Threonate + Magnesium Oxide
Two forms of magnesium
Safety
Medications & health conditions
Magnesium reduces levothyroxine absorption. Magnesium binds levothyroxine in the gut and can lower thyroid hormone levels. Keep it at least 4 hours away from your thyroid medication.
Magnesium blocks absorption of these antibiotics. Magnesium binds tetracycline and quinolone antibiotics in the gut, which can make the antibiotic less effective. Typically take the antibiotic at least 2 hours before or 4–6 hours after magnesium — the exact spacing depends on the drug, so follow its label.
Magnesium can build up with kidney disease. The kidneys remove excess magnesium. With reduced kidney function, supplements can cause dangerous hypermagnesemia.
PPIs can lower magnesium. Long-term PPI use is linked to low blood magnesium. That's a reason to have your level checked, not a reason to avoid magnesium.
Magnesium blocks HIV integrase inhibitors. The labels advise taking dolutegravir or bictegravir 2 hours before or 6 hours after products containing magnesium.
Buying guide
What to look for on the label
Magnesium L-Threonate
- Magtein® (the studied ingredient)
- Labels often show the threonate compound (about 2 g/day), which is under 10% magnesium
FAQ
Common questions
When is the best time to take Magnesium L-Threonate?
Bedtime. Commonly taken in the evening, sometimes split morning and evening.
Should Magnesium L-Threonate be taken with food?
It can be taken with or without food. Commonly taken in the evening, sometimes split morning and evening.
Can you take Magnesium L-Threonate with Calcium?
Yes, at normal doses. At high calcium doses, spacing them out is a reasonable precaution. No action needed at typical doses. If you take ≥1,000 mg calcium from supplements, take magnesium at a different time (e.g. bedtime).
Can you take Magnesium L-Threonate with Zinc?
Yes — this only matters at very high zinc doses. Keep zinc within the 40 mg/day upper limit.
Can you take Magnesium L-Threonate with Vitamin D3?
Yes — adequate magnesium helps vitamin D work, especially at higher D doses. Make sure magnesium intake is adequate if you take vitamin D, especially at higher doses. They do not need to be taken at the same time.
Can you take Magnesium L-Threonate with Psyllium Husk?
Separate them by about 2 hours. Take psyllium at least 2 hours apart from magnesium.
Sources
References
- 01Slutsky I et al. Enhancement of learning and memory by elevating brain magnesium. Neuron 2010.
- 02Hausenblas HA et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial (industry-sponsored). Sleep Med X 2024.
- 03NIH Office of Dietary Supplements — Magnesium Fact Sheet for Health Professionals