Magnesium for sleep: what the evidence shows

The short answer

Magnesium may help a little with sleep, especially if your diet is low in it, but the trials are small and the effects modest. UK and EU law do not allow any brand to claim that magnesium improves sleep. If you want to try it, take bisglycinate or citrate, up to 250 mg of magnesium a day from the supplement, for at least 4 weeks, and judge whether it makes a difference. If you have slept badly for more than three months, see your GP: chronic insomnia has treatments with far stronger evidence.

What the studies show

The pattern is consistent: a small effect, measured mostly by questionnaires, in short and small studies. The authors of the 2025 trial call the improvement modest and ask for studies with objective sleep measurements.

What the law allows on the label

In the UK and the EU, magnesium has the same authorised claims: it contributes to the reduction of tiredness and fatigue, normal nervous system and muscle function, and normal psychological function. None mentions sleep.

The only authorised sleep claim belongs to melatonin: it contributes to reducing the time taken to fall asleep, at 1 mg shortly before bedtime. That is why many “sleep” products sold in the EU combine magnesium with melatonin. In the UK those combinations cannot legally be sold as supplements, because melatonin is a prescription-only medicine; in 2025 the MHRA recalled children’s “magnesium” gummies that turned out to contain melatonin. A magnesium-only pack promising “better sleep” is going beyond what the law allows. See our table of approved health claims and our melatonin guide.

How to take it if you want to try

1. Form: bisglycinate or citrate. Both are absorbed better than oxide and usually well tolerated. More in our guide to magnesium forms.
2. Dose: 100–250 mg of elemental magnesium a day. EFSA’s upper level for magnesium from supplements is 250 mg; the NHS says 400 mg or less is unlikely to cause harm. Above those amounts, diarrhoea becomes more likely.
3. Timing: afternoon or evening, as in the studies. Germany’s BfR advises splitting the daily amount into at least two doses.
4. Duration: at least 4 weeks before deciding whether it works.
5. Check your diet: nuts, legumes, whole grains, cocoa and leafy greens all supply magnesium. If you already eat plenty, a supplement probably adds little.

Talk to your GP or pharmacist first if you have kidney disease, or take bisphosphonates, tetracycline or quinolone antibiotics, diuretics or proton pump inhibitors long term.

If magnesium is not enough

Supplements do not replace what works best for sleep: regular sleep times, daylight in the morning, less caffeine after midday and fewer screens before bed. For chronic insomnia, cognitive behavioural therapy for insomnia (CBT-I) is the first-line treatment in the 2023 European Insomnia Guideline, and the NHS says a GP may offer CBT, face to face or through an online programme. GPs now rarely prescribe sleeping pills.

Our goal finder compares the evidence for magnesium with other sleep options such as melatonin, L-theanine and ashwagandha.