Magnesium bisglycinate is magnesium bound to two molecules of the amino acid glycine. In the one randomised trial of this form for sleep, four weeks of supplementation produced a small but measurable improvement in insomnia scores compared with placebo (Schuster et al., 2025). Across magnesium research as a whole the picture is mixed, and the people most likely to benefit appear to be those who do not get enough from food.
This article covers what the studies show, why the form matters, and how much is sensible to take.
What is magnesium bisglycinate?
Magnesium is a mineral your body uses in the nervous system, in muscles and in energy production. Supplements supply it in different forms: inorganic salts such as magnesium oxide, and organic forms such as citrate and bisglycinate.
In bisglycinate, each magnesium atom is attached to two glycine molecules. This is sometimes called a chelate. You may also see it labelled as magnesium glycinate or diglycinate.
Elemental magnesium: the number that matters
A capsule containing 1,000mg of magnesium bisglycinate does not contain 1,000mg of magnesium. Most of that weight is glycine. The figure to look for is elemental magnesium, the amount of the mineral itself. OFFLINE Sleep provides 135mg of elemental magnesium per serving.
Are people in the UK low in magnesium?
Many are, at least on paper. The UK reference intake is 300mg a day for men and 270mg for women. In the latest National Diet and Nutrition Survey, adults aged 19 to 64 averaged 248mg a day from food, and 17% had intakes below the lower reference nutrient intake, the level considered inadequate for most people (Office for Health Improvement and Disparities, 2025).
A low intake is not the same as a clinical deficiency. It does suggest that a meaningful share of adults have room to top up.
What the research says about magnesium and sleep
The bisglycinate trial
The most relevant study randomised 155 adults with self-reported poor sleep to 250mg of elemental magnesium as bisglycinate or a placebo, taken 30 to 60 minutes before bed for four weeks. Insomnia Severity Index scores fell by 3.9 points with magnesium and 2.3 with placebo. The difference was statistically significant (p = 0.049) and the authors described it as a modest benefit (Schuster et al., 2025).
Two caveats are worth knowing. The dose was 250mg, almost double what OFFLINE Sleep contains. And an exploratory analysis hinted that people with lower dietary magnesium responded more, though this needs confirming.
Older trials with other forms
- In 46 older adults with insomnia, 500mg of magnesium a day as oxide for eight weeks improved insomnia scores, sleep efficiency and time to fall asleep compared with placebo. Melatonin rose and cortisol fell (Abbasi et al., 2012).
- In 12 healthy older adults, a high dose of magnesium for 20 days increased deep slow-wave sleep and lowered night-time cortisol (Held et al., 2002).
- In 100 adults over 51 with poor sleep, 320mg a day as citrate for seven weeks improved sleep scores, but so did placebo, by the same amount (Nielsen, Johnson and Zeng, 2010).
What the reviews conclude
A meta-analysis of three trials in older adults found that magnesium shortened the time taken to fall asleep by about 17 minutes compared with placebo. The authors rated the evidence as low to very low quality (Mah and Pitre, 2021).
A systematic review of nine studies found that observational research links magnesium status to sleep quality, while randomised trials gave contradictory results (Arab et al., 2023). The most recent review, covering 12 randomised trials, reached a similar verdict: results are inconsistent, some adults may see modest benefit on self-rated sleep, and the evidence does not support magnesium as a routine treatment for insomnia (Lopresti, Smith and Drummond, 2026).
Diet and sleep over time
In a study that followed 3,964 American adults, those with the highest magnesium intake were less likely to sleep under seven hours a night than those with the lowest. The link with sleep quality was borderline (Zhang et al., 2022). Studies like this cannot separate magnesium from the generally better diets of people who eat more of it.
How might magnesium help?
Several mechanisms have been proposed. None is firmly proven in people.
- GABA. In laboratory studies, magnesium at physiological concentrations strengthens the response of GABA-A receptors, the brain's main calming system (Möykkynen et al., 2001).
- Stress hormones. Two small trials in older adults reported lower cortisol with magnesium (Held et al., 2002; Abbasi et al., 2012).
- Melatonin. One trial found higher blood melatonin after eight weeks (Abbasi et al., 2012).
These fit the idea that magnesium supports the body's wind-down. They come from cell studies and small trials at high doses, so they are best read as plausible explanations.
Why bisglycinate and not oxide or citrate?
Absorption. A systematic review of 14 studies concluded that inorganic forms such as oxide appear less bioavailable than organic forms (Pardo et al., 2021). In a 60-day trial, magnesium citrate and an amino-acid chelate were both absorbed better than oxide, which performed no better than placebo. Citrate did best on blood and saliva measures (Walker et al., 2003).
So organic forms beat oxide. There is no good head-to-head evidence that bisglycinate beats citrate, and we would not claim it does.
Tolerance. The main side effect of magnesium supplements is loose stools. In a study of patients with bowel resection, magnesium diglycinate was absorbed as well as oxide overall, markedly better in those who absorbed oxide poorly, and was better tolerated (Schuette, Lashner and Janghorbani, 1994).
The glycine. Glycine has sleep research of its own. Three grams before bed improved self-rated sleep quality and shortened time to fall asleep in people with unsatisfying sleep (Yamadera et al., 2007), and reduced next-day fatigue in sleep-restricted volunteers (Bannai et al., 2012). In rats, glycine promotes sleep partly by lowering core body temperature (Kawai et al., 2015).
A serving of magnesium bisglycinate supplying 135mg of magnesium carries roughly 0.8g of glycine, well short of the 3g used in those studies. The glycine is a bonus, not a reason to expect the same results.
How much should you take, and when?
Sleep trials have used between 250 and 729mg of elemental magnesium a day. Typical supplements provide 100 to 250mg.
OFFLINE Sleep contains 135mg. No trial has tested that exact amount for sleep, and we chose it as a top-up to diet alongside four other ingredients, not as a stand-alone treatment dose. For someone eating 250mg a day from food, it brings total intake above the UK reference intake.
On timing, the bisglycinate trial dosed 30 to 60 minutes before bed (Schuster et al., 2025), which matches how we suggest taking OFFLINE Sleep.
Is it safe?
UK guidance is that 400mg a day or less of magnesium from supplements is unlikely to cause harm, with mild diarrhoea reported in a small number of people at around that level (Expert Group on Vitamins and Minerals, 2003). The European upper level for supplemental magnesium is 250mg a day (Scientific Committee on Food, 2001). A 135mg dose sits below both.
Check with a doctor or pharmacist first if you:
- have kidney disease, since the kidneys clear excess magnesium
- take tetracycline antibiotics, whose absorption magnesium can reduce (Gröber, 2019)
- take other regular medication, or are pregnant or breastfeeding
Long-term use of diuretics and proton-pump inhibitors can lower magnesium levels, which is worth raising with your GP (Gröber, 2019).
Frequently asked questions
Is magnesium glycinate the same as bisglycinate? Yes. Glycinate, bisglycinate and diglycinate are names for the same compound.
How long does it take to work? Trials have run for four to eight weeks. The bisglycinate trial measured its effect at four weeks (Schuster et al., 2025).
Why did the magnesium I tried before do nothing? Possibly the form. Magnesium oxide, common in cheaper products, performed no better than placebo for absorption in one trial (Walker et al., 2003). It is also possible you already get enough from food.
Will it make me groggy? Magnesium is not a sedative. In the bisglycinate trial, 93% of participants reported no side effects (Schuster et al., 2025).
The bottom line
Magnesium is not a sleeping pill, and the research does not support it as a cure for insomnia. A well-absorbed form may modestly improve sleep for some people, particularly those whose diets run low, and it is safe at sensible doses. That is why we use bisglycinate in OFFLINE Sleep, and why it is one of five ingredients and not the whole formula.
This article is for general information and is not medical advice. Food supplements are not a substitute for a varied diet. If you have ongoing sleep problems, speak to your GP.
References
Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M.M., Hedayati, M. and Rashidkhani, B. (2012) 'The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial', Journal of Research in Medical Sciences, 17(12), pp. 1161–1169.
Arab, A., Rafie, N., Amani, R. and Shirani, F. (2023) 'The role of magnesium in sleep health: a systematic review of available literature', Biological Trace Element Research, 201(1), pp. 121–128. doi:10.1007/s12011-022-03162-1.
Bannai, M., Kawai, N., Ono, K., Nakahara, K. and Murakami, N. (2012) 'The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers', Frontiers in Neurology, 3, 61. doi:10.3389/fneur.2012.00061.
Expert Group on Vitamins and Minerals (2003) Safe upper levels for vitamins and minerals. London: Food Standards Agency.
Gröber, U. (2019) 'Magnesium and drugs', International Journal of Molecular Sciences, 20(9), 2094. doi:10.3390/ijms20092094.
Held, K., Antonijevic, I.A., Künzel, H., Uhr, M., Wetter, T.C., Golly, I.C., Steiger, A. and Murck, H. (2002) 'Oral Mg2+ supplementation reverses age-related neuroendocrine and sleep EEG changes in humans', Pharmacopsychiatry, 35(4), pp. 135–143. doi:10.1055/s-2002-33195.
Kawai, N., Sakai, N., Okuro, M., Karakawa, S., Tsuneyoshi, Y., Kawasaki, N., Takeda, T., Bannai, M. and Nishino, S. (2015) 'The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus', Neuropsychopharmacology, 40(6), pp. 1405–1416. doi:10.1038/npp.2014.326.
Lopresti, A.L., Smith, S.J. and Drummond, P.D. (2026) 'Magnesium supplementation for sleep in adults: a systematic review of randomized controlled trials', Journal of Dietary Supplements, 23(5), pp. 553–581. doi:10.1080/19390211.2026.2719670.
Mah, J. and Pitre, T. (2021) 'Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis', BMC Complementary Medicine and Therapies, 21(1), 125. doi:10.1186/s12906-021-03297-z.
Möykkynen, T., Uusi-Oukari, M., Heikkilä, J., Lovinger, D.M., Lüddens, H. and Korpi, E.R. (2001) 'Magnesium potentiation of the function of native and recombinant GABA(A) receptors', Neuroreport, 12(10), pp. 2175–2179. doi:10.1097/00001756-200107200-00026.
Nielsen, F.H., Johnson, L.K. and Zeng, H. (2010) 'Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep', Magnesium Research, 23(4), pp. 158–168. doi:10.1684/mrh.2010.0220.
Office for Health Improvement and Disparities (2025) National Diet and Nutrition Survey 2019 to 2023: report. Available at: https://www.gov.uk/government/statistics/national-diet-and-nutrition-survey-2019-to-2023 (Accessed: 13 October 2026).
Pardo, M.R., Garicano Vilar, E., San Mauro Martín, I. and Camina Martín, M.A. (2021) 'Bioavailability of magnesium food supplements: a systematic review', Nutrition, 89, 111294. doi:10.1016/j.nut.2021.111294.
Schuette, S.A., Lashner, B.A. and Janghorbani, M. (1994) 'Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection', Journal of Parenteral and Enteral Nutrition, 18(5), pp. 430–435. doi:10.1177/0148607194018005430.
Schuster, J., Cycelskij, I., Lopresti, A. and Hahn, A. (2025) 'Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial', Nature and Science of Sleep, 17, pp. 2027–2040. doi:10.2147/NSS.S524348.
Scientific Committee on Food (2001) Opinion of the Scientific Committee on Food on the tolerable upper intake level of magnesium. SCF/CS/NUT/UPPLEV/54 Final. Brussels: European Commission.
Walker, A.F., Marakis, G., Christie, S. and Byng, M. (2003) 'Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study', Magnesium Research, 16(3), pp. 183–191.
Yamadera, W., Inagawa, K., Chiba, S., Bannai, M., Takahashi, M. and Nakayama, K. (2007) 'Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes', Sleep and Biological Rhythms, 5(2), pp. 126–131. doi:10.1111/j.1479-8425.2007.00262.x.
Zhang, Y., Chen, C., Lu, L., Knutson, K.L., Carnethon, M.R., Fly, A.D., Luo, J., Haas, D.M., Shikany, J.M. and Kahe, K. (2022) 'Association of magnesium intake with sleep duration and sleep quality: findings from the CARDIA study', Sleep, 45(4), zsab276. doi:10.1093/sleep/zsab276.