Magnesium for Sleep: What the Evidence Actually Says

Magnesium is involved in over 300 enzymatic reactions, including the regulation of GABA — the calming neurotransmitter that quietens the nervous system at bedtime. That is the mechanism the supplement industry leans on. The evidence is more modest than the marketing.

When magnesium helps

• If you are genuinely deficient — common in the elderly, in heavy coffee drinkers, and in people on diuretics.
• If your insomnia includes muscle restlessness or nocturnal cramps.
• If you experience anxiety-led sleep onset difficulty.

When it does not

If your diet already includes leafy greens, nuts and whole grains, you are likely sufficient and the supplement will do little.

Which form to choose

Magnesium glycinate or magnesium threonate are absorbed well and gentle on the gut. Avoid magnesium oxide — cheap, poorly absorbed, and the form most likely to give you digestive trouble before bed.

Dose and timing

200–400 mg of elemental magnesium, 60–90 minutes before bed. Higher doses do not work better; they just shorten the distance to the bathroom.