Magnesium L-Threonate Dosing and Usage
For magnesium deficiency, magnesium L-threonate should be dosed at 2000 mg daily (providing approximately 144 mg elemental magnesium), which is well below the tolerable upper limit of 350 mg from supplements and has demonstrated safety and efficacy in clinical trials. 1, 2
Recommended Dosage
The maximum safe intake of magnesium L-threonate is 3000 mg per day for adults (excluding pregnant and lactating women), which provides approximately 250 mg elemental magnesium—matching the tolerable upper limit for supplemental magnesium from readily dissociable salts. 1
The clinically studied dose is 2000 mg daily (2 g/day), administered as divided doses, which has demonstrated cognitive benefits and safety in healthy adults over 30 days. 2
Start with the recommended daily allowance (320 mg elemental magnesium for women; 420 mg elemental magnesium for men) and increase gradually according to tolerance, though magnesium L-threonate at 2000 mg daily provides only 144 mg elemental magnesium—below the RDA. 3
Unique Properties of L-Threonate
Magnesium L-threonate is superior to other magnesium salts because the threonate component directly elevates intraneuronal magnesium concentration through glucose transporters (GLUTs), a mechanism not shared by other magnesium anions. 4
L-threonate is naturally present in cerebrospinal fluid, and oral administration elevates CSF threonate levels, allowing magnesium to cross the blood-brain barrier more effectively than standard magnesium salts. 4
The threonate component independently upregulates NMDA receptor expression, boosts mitochondrial membrane potential, and increases functional synapse density—effects unique to threonate that explain why magnesium given without threonate is ineffective for cognitive enhancement. 4
Critical Safety Considerations
Check renal function before initiating any magnesium supplementation—creatinine clearance <20 mL/min is an absolute contraindication due to life-threatening hypermagnesemia risk. 3
Exercise extreme caution when creatinine clearance is 20-30 mL/min, and use reduced doses with close monitoring when creatinine clearance is 30-60 mL/min. 3
The novel food contains up to 1% oxalic acid (maximum 30 mg daily exposure), which is not a safety concern at this level. 1
The maximum daily intake of L-threonate from this supplement (2730 mg) matches the safe intake level established in 2008, confirming safety at proposed doses. 1
Administration Strategy
Divide the 2000 mg daily dose into multiple administrations throughout the day to maintain stable magnesium levels, rather than single dosing. 3
For patients with gastrointestinal disorders or malabsorption, magnesium L-threonate may be preferable to magnesium oxide, which causes osmotic diarrhea and is poorly absorbed. 3
Liquid or dissolvable forms are generally better tolerated than pills for all magnesium supplements. 3
Monitoring Protocol
Check baseline serum magnesium, potassium, calcium, and renal function before starting supplementation. 3
Recheck magnesium levels 2-3 weeks after starting supplementation or after any dose adjustment. 3
Once on stable dosing, monitor magnesium levels every 3 months, with more frequent monitoring if high gastrointestinal losses, renal disease, or medications affecting magnesium are present. 3
Monitor for gastrointestinal side effects including diarrhea, abdominal distension, and nausea, though magnesium L-threonate causes less osmotic diarrhea than magnesium oxide. 3
Special Clinical Contexts
For patients with documented magnesium deficiency and concurrent hypokalemia, correct volume depletion with IV saline first to address secondary hyperaldosteronism, then normalize magnesium before expecting potassium supplementation to be effective. 3
In patients with QTc prolongation >500 ms or cardiac arrhythmias, target magnesium >2 mg/dL regardless of baseline level as an anti-torsadogenic measure—this may require higher doses or IV supplementation rather than oral magnesium L-threonate alone. 3, 5
For severe symptomatic magnesium deficiency with neuromuscular irritability or cardiac manifestations, initiate IV magnesium sulfate (1-2 g over 15 minutes for acute severe deficiency) before transitioning to oral magnesium L-threonate for maintenance. 3, 6
Common Pitfalls to Avoid
Do not assume serum magnesium accurately reflects total body magnesium status—less than 1% of magnesium stores are in the blood, with the remainder in bone, soft tissue, and muscle. 5, 6
Do not supplement magnesium without first correcting volume depletion in patients with diarrhea or high-output stomas, as ongoing hyperaldosteronism will cause continued renal magnesium wasting despite supplementation. 3
Do not use magnesium L-threonate as monotherapy for severe, symptomatic magnesium deficiency requiring urgent correction—the relatively low elemental magnesium content (144 mg per 2000 mg dose) makes it unsuitable for rapid repletion. 1, 2
Do not overlook concurrent hypokalemia and hypocalcemia, which are frequently associated with hypomagnesemia and require simultaneous correction. 3, 6