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Magnesium for sleep: which type to choose, how much to take and what the evidence says

Magnesium for sleep is usually glycinate or bisglycinate: magnesium bound to glycine. What the evidence says (a small effect), how much to take according to the NIH and how to read the label.

What magnesium for sleep is for

Magnesium is a mineral the body needs for muscles, nerves and hundreds of other processes. «Magnesium for sleep» is usually glycinate or bisglycinate: magnesium bound to glycine, an amino acid, sold as capsules or powder. It is not a sleeping pill: it is a mineral supplement.

The reason it's recommended is that some people sleep better taking it. But the effect studies have measured is small, so it helps to know what to expect first.

Our pick

Nature's Bounty: magnesium 500 mg, high potency tablets

According to the listing, coated magnesium tablets with 500 mg each (119% of the daily value), gluten-free and without artificial flavors or sweeteners. The listing pitches it for bones, muscles and energy. It's an example of how to read the label: a single tablet is already over 350 mg.

Check before you buy

The form of magnesium (oxide, citrate, glycinate…): read it on the label's ingredient list, because the listing's points don't say.
That one tablet holds 500 mg of magnesium, above the 350 mg a day limit the NIH sets for magnesium from supplements: read the dose the label gives and, if in doubt, ask your doctor.
That the listing pitches it for bones, muscles and energy, not for sleep: there's no sleep trial on this product.
The number of tablets in the pack: the link opens one specific version and the image shows a 200-count bottle.
The return policy for THIS item before you pay.

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What the evidence says

The most recent glycinate trial was randomized and placebo-controlled, with 155 adults who said they slept poorly. They took 250 mg of elemental magnesium a day, as bisglycinate, or a placebo. At four weeks insomnia severity improved by a small but statistically significant amount (p = 0.049). The authors themselves note that participants were still in the mild insomnia range, so the supplement alone is unlikely to remove it.

A 2021 review pooled three trials with 151 older adults comparing oral magnesium with placebo, and other reviews conclude that larger trials are needed to confirm efficacy and learn which form and dose work best. In short: the evidence is modest and mixed, and nearly all of it on glycinate comes from a single trial.

Glycinate, citrate, oxide or threonate

Glycinate or bisglycinate: it's the form most recommended for sleep and usually the gentlest on the stomach, according to consumer and pharmacy sources; no studies compare it head to head with the others.

Citrate and oxide: both can have a laxative effect, especially at high doses, because they draw water into the gut. L-threonate is promoted for brain and sleep, but the evidence we saw is preliminary. Choose by what your stomach tolerates and what the label says.

How much to take

First, what you need in total: the NIH recommended intake for adult women is 310 to 320 mg of magnesium a day (350 to 360 mg in pregnancy), counting food and supplements together. The upper safety limit for magnesium from supplements is 350 mg a day for adults. Food has no such limit because the kidneys clear the excess.

The glycinate trial used 250 mg of elemental magnesium. Note that «elemental»: the label may show the weight of the whole compound (for example 1,000 mg of magnesium bisglycinate), which contains much less magnesium. What counts is the elemental magnesium per serving and how many capsules make a serving.

Consumer guides usually suggest taking it an hour before bed, but we haven't seen studies comparing times. If you start, begin with a low dose and see how it sits.

How to read the label

1. Elemental magnesium per serving, in mg, and how many capsules make a serving.

2. The form: glycinate or bisglycinate, citrate, oxide, threonate.

3. Extras: many «sleep» products add melatonin, ashwagandha, L-theanine or others. If they do, you won't know what's working and you add side effects; magnesium alone is easier to judge.

4. A third-party testing seal, if there is one, and the cost per mg of elemental magnesium, not the price of the bottle.

Side effects and precautions

At high doses, magnesium from supplements can cause diarrhea, nausea and abdominal cramps. If you have kidney disease, take medication (some antibiotics and osteoporosis treatments, for example, can interact with magnesium) or are pregnant or breastfeeding, check with your doctor first.

If you've been sleeping badly for weeks, magnesium is no substitute for a visit: insomnia can have causes worth checking with a professional, besides habits like schedule, caffeine, screens and light at night.