Mineral
Magnesium L-Threonate
Moderate EvidenceThe form is specifically studied for raising brain magnesium in animal work, and a small number of human trials report cognitive effects; the evidence is far lighter than for magnesium repletion generally, hence Moderate.
Recommended Dose
2000 mg (providing ~144 mg elemental Mg) daily
Timing
Evening, split into 2 doses
Mechanism of Action
The only magnesium form clinically demonstrated to cross the blood-brain barrier and elevate brain magnesium levels. Enhances synaptic density in the prefrontal cortex and hippocampus.
Side Effects & Safety
Headache, drowsiness, or GI upset. Lower elemental magnesium per capsule means more pills needed. More expensive than other forms. Avoid in significant kidney impairment, exactly as with any magnesium salt.
Do not use / talk to a doctor first
- Chronic kidney disease or any significant renal impairment - it is still magnesium, cleared by the same route
- Heart block or myasthenia gravis, without medical advice
Interactions
Tetracycline antibiotics (doxycycline, demeclocycline)
Magnesium forms insoluble complexes with them, reducing absorption of the antibiotic. Separate the doses
Source: NIH Office of Dietary Supplements, Magnesium
Quinolone antibiotics (ciprofloxacin, levofloxacin)
Same insoluble-complex problem as tetracyclines. Separate the doses
Source: NIH Office of Dietary Supplements, Magnesium
Oral bisphosphonates (e.g. alendronate)
Magnesium reduces their absorption. Take magnesium at least 2 hours before or after the bisphosphonate
Source: NIH Office of Dietary Supplements, Magnesium
Anything that impairs kidney function
Magnesium is cleared renally. When clearance falls, supplemental magnesium accumulates and hypermagnesemia becomes possible - this, not the upper intake level, is the real hazard
Source: NIH Office of Dietary Supplements, Magnesium
Pregnancy & breastfeeding
Not specifically studied in pregnancy in this form. Magnesium itself is used in pregnancy, but agree any supplement with a midwife or doctor.
Who should avoid / see a doctor
Anyone with reduced kidney function - this entry previously carried no renal caution while the glycinate entry did, which was inconsistent: it is the same mineral cleared the same way. At roughly 144 mg elemental magnesium the dose here sits well under the 350 mg/day supplemental upper intake level, so the tolerability concern is smaller than for high-dose forms; the renal one is identical.
Synergies
Used in These Stacks
See Magnesium L-Threonate inside a full protocol — the stack pages cover when and why to combine it.
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References
- 1.NIH Office of Dietary Supplements, Magnesium - Health Professional Fact Sheet — The tolerable upper intake level for SUPPLEMENTAL magnesium in adults is 350 mg/day. Toxicity risk rises with impaired renal function; signs generally appear once serum concentrations exceed 1.74-2.61 mmol/L. Magnesium forms insoluble complexes with tetracyclines and quinolones and reduces bisphosphonate absorption. (authoritative body)
- 2.Costello 2023, Advances in Nutrition — The 350 mg/day UL was set in 1997 with diarrhea as the limiting factor. Reviewing intervention studies from 1997-2022, seven studies at intakes of 128-1200 mg/day found no significant difference in diarrhea between intervention and control, and an FDA CAERS search found only 40 attributable gastrointestinal adverse-event cases; the authors conclude the UL should be re-evaluated. (perspective / evidence review)
