Best Magnesium L-Threonate Supplements for Cognitive Aging in 2026

Magnesium L-threonate is well-tolerated in clinical trials. At the standard dose (2,000mg salt = ~144–200mg elemental magnesium daily), it provides a moderate magnesium dose that is well within safe upper intake levels. Magnesium in any form can cause loose stools or diarrhea at higher doses — though L-threonate is gentler than oxide or citrate in this regard for most users. Important distinction from other magnesium pages: magnesium L-threonate should not be used as your primary magnesium supplement if you have systemic magnesium deficiency. The elemental magnesium content is relatively low (144–200mg), and the compound is expensive for systemic repletion. Use magnesium glycinate or malate for general magnesium deficiency, and add L-threonate if CNS-specific benefits are the goal. Magnesium may reduce absorption of certain antibiotics (tetracyclines, fluoroquinolones) and bisphosphonate medications — take these at least 2 hours apart. If you have kidney disease, check with your physician before any magnesium supplementation as kidneys regulate magnesium excretion. Always consult your healthcare provider before starting magnesium L-threonate. **Medication and diagnosis boundary:** This supplement is not a replacement for prescription medication, medical evaluation, lab testing, or disease-specific care. If you have a diagnosed condition, take prescription medication, are pregnant or breastfeeding, or have kidney/liver disease, discuss use with your clinician before starting. **Magnesium-specific cautions:** The adult tolerable upper intake level for supplemental magnesium is 350mg/day unless supervised. Separate magnesium from levothyroxine, tetracycline/fluoroquinolone antibiotics, and bisphosphonates. Avoid unsupervised magnesium supplementation in advanced kidney disease or eGFR below 30 mL/min/1.73m2. **Blood thinners:** If you take blood-thinning medications (e.g., warfarin, apixaban, rivaroxaban, clopidogrel, or high-dose aspirin), consult your healthcare provider BEFORE starting this supplement, as it may have additive antiplatelet or anticoagulant effects. **Gout:** Individuals with gout should consult their healthcare provider before starting this supplement. Certain supplements (e.g., collagen, fish oil, niacin) may affect uric acid levels or trigger flares in susceptible individuals. **Blood pressure medications:** If you take antihypertensive medications (e.g., ACE inhibitors, ARBs, beta-blockers, calcium-channel blockers, or diuretics), consult your healthcare provider before starting magnesium L-threonate, as it may have additive blood-pressure-lowering effects and require dose monitoring.