Magnesium glycinate and sleep

The question

Magnesium glycinate is one of the most popular choices for sleep, and in 2025 it was tested in a placebo-controlled trial larger than earlier magnesium and sleep trials. That trial found a statistically significant improvement in insomnia symptoms compared with placebo, and the magnesium was well tolerated. This review looks at what the trial did, what it found, and where it fits in the wider research.

The evidence in brief

• An encouraging first trial. In 155 adults reporting poor sleep, insomnia scores fell further on magnesium bisglycinate than on placebo over four weeks, with most of the improvement in the first two weeks.
• More people reached a meaningful improvement. 26 people on magnesium reached the researchers' threshold for a clinically significant improvement, compared with 15 on placebo.
• Well tolerated. 93% of participants reported no adverse events, and side effects were less common on magnesium than on placebo.
• A modest effect. The researchers described the effect as small, and other measures, including sleep quality, did not differ from placebo.
• Part of a developing field. Systematic reviews rate the overall evidence on magnesium and sleep as low to very low certainty, and a 2026 review concluded that current evidence does not support oral magnesium as a routine treatment for insomnia.

The 2025 magnesium bisglycinate trial

What the researchers did

The trial was a randomised, double-blind, placebo-controlled study run across Germany, with participants taking part from home and completing questionnaires online.

It enrolled 155 adults aged 18 to 65 who reported poor sleep for more than four weeks and described themselves as otherwise healthy. People with diagnosed sleep disorders such as sleep apnoea, shift workers, people with serious chronic illness, people taking medicines that affect sleep or mood, and people who were pregnant or breastfeeding were excluded.

Participants took two capsules a day, 30 to 60 minutes before bed, for four weeks. The magnesium capsules together supplied 250 mg of elemental magnesium and about 1.5 g of glycine a day, as magnesium bisglycinate. The placebo capsules contained cellulose and looked identical. The capsules were made by a commercial supplement manufacturer.

The main outcome was the Insomnia Severity Index, a widely used seven-item questionnaire about sleep difficulty, satisfaction with sleep, and its effect on daytime life. The researchers also measured sleep quality, fatigue, daytime sleepiness, stress, mood and anxiety and depression symptoms, all by questionnaire.

What they found

The main outcome. Insomnia Severity Index scores fell further on magnesium than on placebo: by an average of 3.9 points against 2.3, or 28% against 18%. The difference reached statistical significance by a narrow margin, and the researchers described the effect size as small.

An analysis limited to the 134 participants who followed the protocol closely found the same pattern, with falls of 5.0 and 3.1 points.

Meaningful improvement. Using a threshold of a 6-point drop on the index, which the researchers treated as clinically significant, 26 people in the magnesium group reached it, compared with 15 in the placebo group.

Timing. Most of the improvement on the main measure appeared within the first two weeks and held for the rest of the trial.

Side effects. No serious adverse events were reported. 93% of participants reported no adverse events, and side effects were less frequent in the magnesium group than the placebo group.

Other measures. None of the other measures showed a significant difference between the groups, including sleep quality, fatigue, daytime sleepiness, perceived stress and mood. Sleep quality improved in both groups in the first week.

Where people ended up. At four weeks, the average score in the magnesium group was still in the range the researchers describe as subthreshold insomnia. In their words, supplementation alone is unlikely to eliminate insomnia for many people.

Strengths and limitations

The trial has real strengths. It was randomised, double-blind and placebo-controlled, it was larger than earlier magnesium and sleep trials, and it was the first to test magnesium glycinate for sleep at all.

Like any single trial, it also has limitations.

• Everything was self-reported. No sleep was measured objectively, with sleep monitoring or wrist-worn devices. A voluntary sleep diary was completed fully by fewer than 10% of participants, too few to analyse.
• The main result was narrow. The difference from placebo only just reached statistical significance, and the effect size was small.
• It was short. Four weeks says nothing about longer-term use.
• Magnesium levels were not measured. The researchers did not test anyone's magnesium status, so the trial cannot say whether people who were low in magnesium responded differently.
• The dietary finding is an early lead. Participants who reported eating fewer magnesium-rich foods improved more. That is an interesting signal, but it was measured with a single unvalidated question, and the researchers flagged it as needing confirmation.
• The magnesium and the glycine were not separated. The trial cannot say how much of any effect came from each.

Does magnesium glycinate make you sleepy?

Not in the way a sleeping tablet does. Magnesium is not a sedative, and the improvement in the trial was a gradual change in insomnia scores over weeks of regular use rather than drowsiness after a dose.

The trial also measured daytime sleepiness directly. It did not differ between the magnesium and placebo groups, so people taking magnesium glycinate before bed were no drowsier during the day than people taking placebo.

Where this trial fits

The 2025 trial is part of a small but growing body of research on magnesium and sleep. A 2021 meta-analysis found that older adults with insomnia fell asleep about 17 minutes faster on magnesium than on placebo, though the evidence was rated low to very low quality. A 2026 review of twelve randomised trials found results varied between studies and rated the certainty of evidence as low to very low. It concluded that current evidence does not support oral magnesium as a routine treatment for insomnia, that it may provide modest benefits for some self-reported outcomes in some adults, and that better trials are needed.

Other forms have been tested too. A 2024 trial of magnesium L-threonate in 80 adults with self-reported sleep problems reported benefits on several measures over 21 days, with three of its six authors affiliated with an ingredient company. It used a different form, so it is not evidence about magnesium glycinate, and no trial has compared the two.

Our review of whether magnesium helps you sleep covers the wider research across every form in more detail.

What about the glycine?

This is one of the more interesting open questions. Magnesium glycinate supplies a substantial amount of glycine, around 1.5 g in the 2025 trial's daily dose. Glycine has been studied separately for sleep, usually at around 3 g, and the trial's authors suggest it could contribute alongside the magnesium.

That remains a hypothesis for now. No trial has tested magnesium glycinate against magnesium and glycine given separately, so any contribution from the glycine is unknown. The same goes for how magnesium might affect sleep: the mechanisms usually proposed come mainly from animal and laboratory research, and have not been confirmed as the explanation for any effect in people.

What this means

Magnesium glycinate has one encouraging placebo-controlled trial behind it for sleep. Adults with self-reported poor sleep who took it for four weeks reported a small but statistically significant improvement in insomnia symptoms beyond placebo, and it was well tolerated. The wider research on magnesium and sleep is still developing, and the most recent review concluded that current evidence does not support magnesium as a routine treatment for insomnia.

It is also worth knowing what the established treatments are. For ongoing insomnia, cognitive behavioural therapy is usually the first treatment recommended when sleep habits and relaxation techniques have not helped. healthdirect notes that there is little scientific evidence about whether over-the-counter sleep remedies work, and recommends talking to your doctor before taking any sleep aid, because some can interact with other medicines.

If poor sleep has lasted more than a few weeks, is affecting your mood or daytime life, or you wake up unrefreshed, speak with your doctor. Poor sleep can have causes that need their own assessment. Our guides to how much magnesium glycinate per day and side effects and interactions cover dosing and who should check before taking magnesium.

We will update this review as new trials are published. Nothing on this page is a substitute for individual medical advice.