Benefits
Sleep quality in adults with poor sleep
In a 4-week placebo-controlled trial of 155 adults reporting poor sleep, 250 mg of magnesium a day as bisglycinate lowered Insomnia Severity Index scores more than placebo (down 3.9 vs 2.3 points). The effect was small, and other sleep, fatigue and mood questionnaires did not differ. People with lower dietary magnesium intake seemed to improve more.
Stress and anxiety
In the 4-week sleep trial, magnesium bisglycinate did not change perceived stress or anxiety and depression screening scores compared with placebo. A 2017 review of 18 studies of magnesium in any form, alone or combined with other ingredients, found results suggesting less self-rated anxiety in people prone to anxiety, but rated the evidence quality as poor.
Muscle cramp frequency
In 80 pregnant women with leg cramps, 300 mg a day of magnesium bisglycinate for 4 weeks cut cramp frequency by at least half in more women than placebo did (86% vs 61%). A 2020 review of 11 trials of magnesium in any form rated the pregnancy trials at high risk of bias, found it unlikely to help older adults with typical night cramps, and found no trials of exercise-related cramps.
Digestive tolerance
In a small crossover study of 12 people with part of the small intestine removed, magnesium diglycinate was better tolerated than magnesium oxide. In the 4-week sleep trial, few adverse events were reported and they were not more common than with placebo. High doses of any magnesium supplement can still cause diarrhea, nausea or cramping.
Magnesium absorption compared with magnesium oxide
In 12 people who had part of the small intestine removed, absorption of a 100 mg labelled dose was similar for the glycinate chelate and magnesium oxide overall (23.5% vs 22.8%). In the 4 people who absorbed oxide most poorly, absorption from the chelate was about twice as high, and it peaked earlier.
Mechanism of action
Absorption as a chelate
In magnesium bisglycinate, magnesium is bound to two glycine molecules. An absorption study suggested that part of the dose is absorbed intact, probably through the dipeptide transport pathway in the small intestine, in addition to the usual mineral routes.
Role in nerve and muscle function
Magnesium is a cofactor in more than 300 enzyme systems, including those for protein synthesis, energy production, and muscle and nerve function. It also helps move calcium and potassium across cell membranes, which matters for nerve signals and muscle contraction.
Why some magnesium forms loosen stools
Unabsorbed magnesium salts draw water into the intestine and speed gut movement, which causes the laxative effect of high doses. The forms most often reported to cause diarrhea are magnesium carbonate, chloride, gluconate and oxide.
Clinical trials
Randomized, double-blind, placebo-controlled trial of magnesium bisglycinate (250 mg elemental magnesium a day) or placebo for 4 weeks, funded by Leibniz University Hannover (Schuster et al. 2025, Nat Sci Sleep)
155 adults aged 18 to 65 reporting poor sleep quality.
Insomnia Severity Index scores fell 3.9 points with magnesium and 2.3 with placebo (p = 0.049), a small effect (d = 0.2). Other sleep, fatigue, perceived stress and mood measures did not differ between groups. No serious adverse events occurred, and adverse events were fewer with magnesium (2) than placebo (7).
Double-blind, randomized, placebo-controlled trial of magnesium bisglycinate chelate 300 mg a day or placebo for 4 weeks (Supakatisant et al. 2015, Matern Child Nutr)
80 healthy pregnant women at 14 to 34 weeks with leg cramps at least twice a week (86 enrolled).
A 50% or greater drop in cramp frequency occurred in 86.0% of the magnesium group vs 60.5% on placebo (P = 0.007), and in cramp intensity in 69.8% vs 48.8% (P = 0.048). Side effects such as nausea and diarrhea did not differ. A later Cochrane review rated this group of pregnancy trials at high risk of bias.
Double-blind, randomized crossover study comparing absorption of a 100 mg dose of isotope-labelled magnesium diglycinate and magnesium oxide (Schuette et al. 1994, JPEN J Parenter Enteral Nutr)
12 adults who had undergone ileal resection.
Overall absorption did not differ (23.5% vs 22.8%). In the 4 patients who absorbed magnesium oxide most poorly, absorption was higher from the chelate (23.5% vs 11.8%, p < .05). The chelate peaked earlier and was better tolerated by all patients.