Magnesium: The Complete Guide

Magnesium is an essential mineral and electrolyte, the fourth most abundant in the human body. It cofactors over 300 enzymatic reactions including ATP synthesis, DNA repair, muscle contraction, and GABA receptor function. Without adequate magnesium, sleep, recovery, and stress resilience all suffer.

Modern diets and depleted soil have reduced magnesium intake dramatically. Processed foods, alcohol, stress, and certain medications (PPIs, diuretics) further deplete stores. Blood serum magnesium is a poor marker, only 1% of body magnesium is in blood, so deficiency can exist with 'normal' labs.

Not all magnesium supplements are equal. The 'form' determines absorption, GI tolerance, and primary effects. Elemental magnesium dose matters, a 400mg capsule of magnesium glycinate contains ~50mg elemental magnesium, not 400mg.

Magnesium glycinate (bisglycinate): bound to glycine, highly absorbable, gentle on gut, promotes relaxation and sleep. Best default choice for most biohackers.

Magnesium threonate (Magtein): crosses the blood-brain barrier more effectively. Marketed for cognitive function and memory. Human data exists but is limited to a few studies, promising, not definitive.

Magnesium citrate: good absorption, osmotic laxative effect at higher doses. Useful if constipated; avoid before bed if GI-sensitive.

Magnesium oxide: cheap, poorly absorbed (~4%), mostly useful as a laxative. Skip for supplementation purposes.

Huberman's commonly cited approach: 300–400mg magnesium glycinate or threonate 30–60 minutes before bed to support sleep onset and depth. Glycinate's glycine component may independently support sleep quality.

For daytime stress or muscle recovery: split dosing, 200mg glycinate morning + 200mg evening. Athletes with heavy training loads may need higher total intake (400–600mg elemental) from food + supplements combined.

Start at 200mg elemental and increase over a week. Loose stools mean you've exceeded your absorption threshold, back off 100mg.

Night 1–3: Subtle relaxation, possibly easier sleep onset. Some feel nothing initially, deficiency severity varies.

Week 1–2: Improved sleep continuity, reduced muscle cramps (especially night cramps), less jaw clenching or tension headaches.

Month 1+: Cumulative benefits for HRV and recovery if deficiency was contributing. Not a sedative, think 'removing a blocker' rather than adding a drug effect.

Excess magnesium from supplements causes diarrhea, the body's primary excretion route. Reduce dose if GI issues occur. Kidney disease patients must avoid unsupervised magnesium supplementation, impaired excretion can cause hypermagnesemia.

Interactions: magnesium can reduce absorption of certain antibiotics (take 2+ hours apart) and may enhance blood pressure medication effects. Consult a pharmacist if on multiple medications.

Safe in pregnancy at RDA levels (350–400mg/day upper limit from supplements per NIH). Glycinate is commonly recommended by obstetricians for leg cramps.

r/Supplements overwhelmingly recommends glycinate for sleep, 'mag glycinate changed my life' is a recurring theme. Threonate divides opinion: believers report focus benefits; skeptics note the cost premium for limited data.

Matthew Walker discusses magnesium's role in sleep architecture. Bryan Johnson's Blueprint includes magnesium in his evening stack. Consensus: fix magnesium before chasing exotic sleep compounds.