Why does the form of Magnesium matter?
Magnesium is the 8th most abundant element on the earth's crust and is found on rocks in its solid form combined with other minerals and metals.5 Our bodies cannot absorb magnesium in its solid form, so it must be paired with a ''carrier'' molecule to ensure it dissolves in the gut. Absorption efficiency, or bioavailability, really depends on how soluble the ''carrier'' molecule is. When the compound hits the gut, the magnesium and ''carrier'' molecule separate and are both absorbed into the blood stream. Each molecule has its own purpose in our metabolism.
Glycinate Vs. Citrate Vs. Threonate
No study has compared magnesium bisglycinate, citrate, and threonate directly against each other, so any attempt to rank the three for the effect on insomnia remains modest. Separate placebo-controlled trials that used different populations, doses, and outcome measures have been conducted. A particular paper analysed three trials and found that sleep onset latency was 17.36 minutes shorter with magnesium than with placebo, while the 16-minute gain in total sleep time was not statistically significant. The authors judged the literature too weak for confident clinical recommendations.1
Glycinate:
Magnesium glycinate, more accurately referred to as magnesium bisglycinate, is a magnesium ion bound to 2 glycine molecules. Glycine is a non-essential amino acid crucial for the synthesis of various biomolecules. Glycine itself has been researched as a micronutrient with anti-inflammatory properties.6 Regarding sleep research a small study on poor sleep, administered 3 g of glycine before bed. It was found to improve how well people felt before they slept, help them fall asleep and reach deep sleep sooner.7 These effects might be due to glycine's ability to lower core body temperature, an essential part of how the body naturally falls asleep.8
A four-week trial enrolled 155 adults aged 18–65 with self-reported poor sleep and gave them 250 mg of elemental magnesium as bisglycinate or placebo. Insomnia Severity Index scores fell by 3.9 points with magnesium versus 2.3 with placebo (p = 0.049), showing a modest improvement in Sleep. 2
Threonate:
Threonate is a natural breakdown product of vitamin C. It became popular after a rat study showed that this form raised magnesium levels in the brain and improved learning and memory. In humans, however, no evidence has shown an increase of magnesium in the brain and threonate has no known application in the metabolism.9
80 adults aged 35–55 with self-reported poor sleep took 1 g/day of magnesium L-threonate or placebo for 21 days, with sleep tracked by questionnaires and an Oura ring. The authors reported better sleep quality, particularly in deep and REM sleep stages, along with improved mood, energy, and alertness. 3
Citrate:
Citrate is the name given to citric acid when it is acting as a ''carrier'' molecule; it is exactly the same substance found in citric fruits. When citrate is processed in the body it is routinely used as fuel for energy.
Magnesium citrate has the weakest sleep-specific evidence. In a trial where adults with poor sleep took 320 mg/day of magnesium as citrate or a placebo for seven weeks, sleep improved in both groups, and the authors concluded that another factor, possibly a placebo effect, improved sleep quality.4
Overall, glycinate has the largest form-specific trial and threonate has promising early data, but neither has been shown to outperform other forms. Any form is most likely to help people who are low in magnesium to begin with.
How does Magnesium deficiency affect sleep?
Early signs of magnesium deficiency include loss of appetite, nausea, fatigue and weakness. More serious deficiency can cause numbness, tingling, cramps and abnormal heart rhythms.10 Adults need 310–420 mg of magnesium a day, depending on age and sex. Nuts, seeds, legumes, leafy greens and whole grains are good dietary sources.10 Low magnesium may also disturb sleep. Magnesium helps calm the nervous system in two ways: it boosts GABA, the brain’s main “slow down” signal, which reduces how excitable nerve cells are, and it blocks NMDA receptors, which drive excitatory activity.11 With too little magnesium, the brain may stay more alert at bedtime.
References
1. Mah, J., & Pitre, T. (2021). Oral magnesium supplementation for insomnia in older adults: A systematic review & meta-analysis. BMC Complementary Medicine and Therapies, 21(1), 125 https://doi.org/10.1186/s12906-021-03297-z
2. Schuster, J., Cycelskij, I., Lopresti, A., & Hahn, A. (2025). Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: A randomized, placebo-controlled trial. Nature and Science of Sleep, 17, 2027–2040. https://pmc.ncbi.nlm.nih.gov/articles/PMC12412596
3. Hausenblas, H. A., Lynch, T., Hooper, S., Shrestha, A., Rosendale, D., & Gu, J. (2024). Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial. Sleep Medicine: X, 8, 100121. https://doi.org/10.1016/j.sleepx.2024.100121
4. Nielsen, F. H., Johnson, L. K., & 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), 158–168. https://pubmed.ncbi.nlm.nih.gov/21199787/
5. U.S. Geological Survey. (n.d.). Magnesium statistics and information. National Minerals Information Center. Retrieved October 9, 2026, from https://www.usgs.gov/centers/national-minerals-information-center/magnesium-statistics-and-information
6. Aguayo-Cerón KA, Sánchez-Muñoz F, Gutierrez-Rojas RA, Acevedo-Villavicencio LN, Flores-Zarate AV, Huang F, Giacoman-Martinez A, Villafaña S, Romero-Nava R. Glycine: The Smallest Anti-Inflammatory Micronutrient. Int J Mol Sci. 2023 Jul 8;24(14):11236. doi: 10.3390/ijms241411236. PMID: 37510995; PMCID: PMC10379184.
7. Yamadera, W., Inagawa, K., Chiba, S., Bannai, M., Takahashi, M., & Nakayama, K. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms, 5(2), 126–131. https://doi.org/10.1111/j.1479-8425.2007.00262.x
8. Bannai, M., & Kawai, N. (2012). New therapeutic strategy for amino acid medicine: Glycine improves the quality of sleep. Journal of Pharmacological Sciences, 118(2), 145–148. https://doi.org/10.1254/jphs.11r04fm
9. Slutsky, I., Abumaria, N., Wu, L.-J., Huang, C., Zhang, L., Li, B., Zhao, X., Govindarajan, A., Zhao, M.-G., Zhuo, M., Tonegawa, S., & Liu, G. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165–177. https://doi.org/10.1016/j.neuron.2009.12.026
10. Office of Dietary Supplements. Magnesium: fact sheet for health professionals [Internet]. Bethesda (MD): National Institutes of Health; [cited 2026 Oct 1]. Available from: https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
11. Arab A, Rafie N, Amani R, Shirani F. The role of magnesium in sleep health: a systematic review of available literature. Biol Trace Elem Res. 2023;201(1):121–8. doi:10.1007/s12011-022-03162-1
