Magnesium glycinate for sleep: what the studies show.

Older adults, several magnesium preparations.

Mah and Pitre's systematic review combined three randomised trials with 151 older adults who had insomnia. The trials studied oral magnesium against placebo, rather than comparing one shop brand with another. They did not provide a clean answer for magnesium glycinate specifically. The pooled result for time taken to fall asleep favoured magnesium by about 17 minutes, but the result comes from a small evidence base. Total sleep time was about 16 minutes longer in the magnesium groups, a difference the analysis did not establish as statistically clear.

The review authors judged all included trials to have moderate to high risk of bias and graded the outcomes low to very low quality. That matters more than a single positive number: a small, uncertain set of trials can overstate an effect, and results in older adults do not automatically apply to younger people with different sleep problems. A 2024 correction amended reporting text and study-flow counts; the published correction did not replace the sleep-outcome estimates above.

A specific bisglycinate trial in adults reporting poor sleep.

Schuster and colleagues enrolled 155 adults aged 18 to 65 who reported poor sleep. In a four-week, double-blind trial, participants were assigned magnesium bisglycinate or matching placebo capsules. The active group received two capsules a day, providing a total of 250 mg elemental magnesium and about 1.52 g glycine. Those are the amounts tested in the study, not a recommended dose or a conversion rule for retail products.

The primary measure was the Insomnia Severity Index, a questionnaire about perceived insomnia symptoms and their effect on daily life. By week four, the mean score fell 3.9 points in the magnesium group and 2.3 points in the placebo group. The between-group comparison met the study's statistical threshold narrowly, with p = 0.049. The authors reported a small effect size, d = 0.2. A statistical difference on this scale does not mean every participant slept better, and it does not describe an objective change in minutes asleep.

The study also measured other questionnaires covering sleep quality, fatigue, mood, stress and daytime sleepiness. These did not show consistent between-group advantages. Fewer than one in ten participants completed enough voluntary sleep diaries for meaningful diary analysis. The trial used self-reported outcomes and did not verify sleep with a wearable or sleep-lab measure. The authors called for longer studies with objective sleep measurements. Their four-week result cannot establish sustained benefit over months or years.

The trial amount was elemental magnesium.

The bisglycinate trial's 250 mg figure refers to elemental magnesium, the magnesium itself. On a retail label, a larger number may refer to the whole magnesium glycinate compound. It cannot be substituted for the trial's elemental figure. A single product may also combine glycinate with other magnesium forms or include other active ingredients. Our table separates verified forms and displays the comparison unit stated on the source page, such as one tablet, two capsules or a measured quantity of powder.

The source-matched pack prices below are for comparison only. A lower cost per 100 mg does not mean stronger sleep evidence. No listed product was tested in either study merely because it contains a similarly named ingredient. We have not scored brands on sleep effect, and a product name containing “sleep” remains a marketing name, not a result from a clinical trial.

The Australian upper level is a separate reference.

The NHMRC Nutrient Reference Values list an upper level of 350 mg a day from supplements for adults aged 19 and over. This limit does not count magnesium naturally present in food, and it is not a target or an instruction to take a supplement. The 250 mg elemental amount in the 2025 study is below that listed adult supplement upper level. It does not follow that the study amount is right for any individual or that adding multiple products is appropriate.

NHMRC uses diarrhoea as the critical endpoint for excess non-food magnesium intake. Medicines, health conditions and other supplements can matter when assessing suitability. The trial excluded people with several chronic conditions, pregnancy or breastfeeding, and regular use of certain medicines. Its results should not be stretched to those groups. Anyone dealing with ongoing insomnia or questions about personal intake should discuss the whole situation with a GP or pharmacist rather than using a product table as treatment advice.