Which magnesium is best?

Glycinate for general use, sleep, and anxiety. Citrate if you’re also constipated. Threonate if specifically targeting cognitive function. Skip oxide regardless of price — the absorption is too low to justify.

How much magnesium per day?

200-400 mg elemental magnesium supplementally, on top of dietary intake. Daily total target: 420 mg for men, 320 mg for women. Most adults get 200-300 mg from diet.

Does magnesium really help sleep?

Modest but real effect, particularly in adults with low baseline status. 200-400 mg of glycinate 30-60 minutes before bed produces measurable improvements in sleep onset and quality at 4-8 weeks.

Will magnesium cause diarrhea?

Citrate often does at higher doses (also used clinically as a laxative). Glycinate is much gentler. Split doses across the day if you notice loose stool.

What about Epsom salt baths?

Transdermal magnesium absorption claims are weak in published evidence. Epsom salts are fine for the relaxing soak effect but don’t produce meaningful magnesium uptake. For supplementation, use oral glycinate or citrate.

Magnesium Glycinate vs. Citrate vs. Oxide: The Forms Ranked by Evidence

The 60-second version

Magnesium form matters more than dose for absorption and tolerability. The published bioavailability evidence ranks them: glycinate, citrate, malate, taurate, and threonate absorb 30-50%; oxide and sulfate absorb 4-10%. The cheap magnesium oxide products that dominate drug-store shelves deliver almost none of the magnesium you pay for. Magnesium glycinate is the best general-purpose form: well-absorbed, gentle on the GI tract, useful for sleep. Magnesium citrate is comparable on absorption but more likely to produce loose stool (also why it’s used as a laxative). Magnesium threonate is the only form that meaningfully crosses the blood-brain barrier — useful if the target is cognitive function. Target intake: 400-420 mg elemental magnesium daily for men, 310-320 mg for women. Most adults get 200-300 mg from diet; supplementation closes the gap.

The forms ranked

Magnesium glycinate (bisglycinate): 30-40% absorption, well-tolerated, ideal for sleep/anxiety/recovery use. Cost: moderate.
Magnesium citrate: 30-40% absorption, mild laxative effect (also used clinically as a laxative at 1500+ mg). Useful if constipation is a concurrent issue.
Magnesium malate: 30-40% absorption, energy/fatigue applications. Slight stimulant feel for some.
Magnesium threonate: 30-40% absorption, crosses blood-brain barrier. Cognitive function applications. Most expensive form.
Magnesium taurate: 30-40% absorption, cardiovascular applications.
Magnesium oxide: 4-10% absorption. Cheap but mostly passes through unabsorbed. Skip.
Magnesium sulfate (Epsom salts): minimal oral absorption; transdermal absorption claims are weak. Useful for laxative or short-term sore-muscle bath, not for chronic supplementation Walker 2003.

What magnesium actually does

Sleep quality. 200-400 mg of glycinate or citrate before bed produces measurable improvements in sleep onset and subjective quality, particularly in adults with low baseline status.
Muscle cramps (modest evidence in adults with documented low magnesium).
Blood pressure in adults with hypertension or pre-hypertension (small but consistent reduction).
Insulin sensitivity — consistent inverse correlation between magnesium intake and type-2 diabetes risk in cohort studies.
Vitamin D activation — magnesium is a cofactor; low magnesium blunts D3 response.
Anxiety/mood — small but consistent trial effects, particularly with glycinate Rondanelli 2021.

“Bioavailable forms of magnesium (glycinate, citrate, malate, threonate) produce 3-5 fold higher absorption than magnesium oxide. Product selection meaningfully affects supplementation outcomes; the cheap-versus-expensive distinction in retail magnesium is real.”
— Walker et al., Magnes Res, 2003 view source

Practical dosing

200-400 mg elemental magnesium daily, taken with food or 30-60 min before bed.
Read the elemental dose, not the compound dose. “500 mg magnesium glycinate” usually means 500 mg of the glycinate compound, containing ~100 mg elemental magnesium.
Split into 2 doses if taking 400+ mg. Single large doses are more likely to produce loose stool.
Take separately from iron and calcium supplements (2-hour spacing) — competitive absorption.
Glycinate for sleep, citrate if also constipated, threonate if cognitive focus, oxide never.

Practical takeaways

Magnesium form matters dramatically: glycinate, citrate, malate, threonate absorb 3-5× better than oxide.
Daily target: 200-400 mg elemental magnesium (men 420, women 320 total intake including diet).
Best general form: glycinate. Sleep-focused: glycinate. Cognitive-focused: threonate. Skip oxide.
Read elemental dose on labels — not compound dose. “500 mg magnesium glycinate” is roughly 100 mg elemental.

References

Walker 2003Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183-191. View source →

Rondanelli 2021Rondanelli M, Faliva MA, Tartara A, et al. An update on magnesium and bone health. Biometals. 2021;34(4):715-736. View source →