Magnesium Bisglycinate (Glycinate) Capsules

Each capsule provides 133 mg of magnesium, which is 35% of the nutrient reference value. Take 1 capsule per day with food, as the label directs. A pot holds 90 capsules, a 90-day supply. The magnesium comes from a blend of magnesium bisglycinate and magnesium oxide in a vegetarian cellulose shell, and the capsules are vegan. Supplement labels state the mineral itself, not the weight of the compound, so 133 mg of magnesium is far more than 133 mg of powder.

Sources: Product label; NIH Office of Dietary Supplements.

Yes: magnesium glycinate and magnesium bisglycinate are the same compound under two names. The prefix "bis" means that each magnesium atom is attached to two glycine molecules, and chemical databases list glycinate, bisglycinate and diglycinate as one substance, so a product labelled either way contains the same thing. Chemists call this kind of bond a chelate. The compound is about one part in seven magnesium by weight: 893 mg of it supplies 125 mg of the mineral. Magnesium L-threonate and magnesium taurate are different compounds, not other names for glycinate, and neither is sold here.

Sources: PubChem, US National Library of Medicine; NIH Office of Dietary Supplements.

Magnesium bisglycinate supplies magnesium, which the body needs for more than 300 enzyme systems. Those enzymes turn food into energy and build protein and DNA. The mineral also moves calcium and potassium across cell membranes, the process behind nerve signals, muscle contraction and a steady heartbeat, and bone contains magnesium as part of its structure. Research on wider effects is mixed: trials of magnesium for blood pressure report reductions of only 2 to 4 mmHg, and the sleep evidence is set out in the next answer.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.

Magnesium bisglycinate is the form most often chosen for evening use, and there is one trial behind that. In 2025, 155 adults with poor sleep took 250 mg of magnesium as bisglycinate for four weeks, as two capsules 30 to 60 minutes before bed, and reported a small improvement over placebo, largest in people who ate little magnesium; the change appeared within the first 14 days and then held steady. Glycine on its own, at 3 g at bedtime, improved sleep quality in small trials. Clinicians suggest 100 to 200 mg of magnesium a night as a reasonable starting amount, which one of these capsules sits inside. The label directs one capsule a day with food, so the evening meal is the natural point.

Sources: Peer-reviewed trial, Nature and Science of Sleep, 2025; Cleveland Clinic; product label.

Magnesium bisglycinate is among the forms least likely to upset the stomach, which is why it is the usual next step after citrate or oxide. Among the others, aspartate, citrate, lactate and chloride dissolve well and are absorbed more completely than oxide or sulfate. A 1994 trial in 12 patients with impaired absorption found bisglycinate and oxide absorbed to a similar degree overall, but bisglycinate was absorbed faster, was tolerated by every patient, and was absorbed about twice as well as oxide in the four patients with the poorest uptake. These capsules combine bisglycinate with oxide, so they are not a pure chelate; the label states the blend and the magnesium figure is the total from both.

Sources: NIH Office of Dietary Supplements; peer-reviewed trial (Schuette and colleagues, 1994); product label.

UK guidance puts the daily amount adults need at 300 mg for men and 270 mg for women, counting food and supplements together. The same guidance says that 400 mg or less a day from supplements is unlikely to cause harm. Safety levels elsewhere are lower: the American upper level for supplemental magnesium is 350 mg a day and the European level 250 mg, both set at the point where loose stools begin. One capsule at 133 mg sits well inside all three. Magnesium can be taken at any time of day, with no published evidence that one time absorbs better than another, and Mayo Clinic advises taking it with meals because magnesium on an empty stomach can cause diarrhoea. Around 30% to 40% of the magnesium in food and supplements is absorbed.

Sources: Food Standards Scotland; NIH Office of Dietary Supplements; EFSA; Mayo Clinic.

Magnesium bisglycinate is commonly taken alongside vitamin D, vitamin B6 and zinc, and research covers each pairing. The body uses magnesium to regulate the active form of vitamin D and parathyroid hormone, so the two are often paired for bone. In a trial of 264 stressed adults, 300 mg of magnesium with 30 mg of vitamin B6 for eight weeks worked no better than magnesium alone overall. Zinc at 142 mg a day, far above any normal supplement, was found to block magnesium absorption. Prescription drugs matter more: magnesium reduces the absorption of oral bisphosphonates and of tetracycline and quinolone antibiotics, so these should be taken at least 2 hours apart, and long-term diuretics and proton pump inhibitors can lower magnesium levels. Anyone on regular prescriptions should ask a pharmacist first.

Sources: NIH Office of Dietary Supplements; peer-reviewed trial (Pouteau and colleagues, PLOS ONE, 2018).

Magnesium bisglycinate has the side effects of magnesium in general, and fewer of them than most forms. High doses of any magnesium supplement can cause diarrhoea, nausea and stomach cramps, because unabsorbed magnesium draws water into the gut; the forms most often reported to do this are carbonate, chloride, gluconate and oxide. In the 2025 trial of 250 mg a day, 93% of participants reported no side effects, and complaints were fewer on magnesium than on placebo. Excess magnesium from food is not a concern, because healthy kidneys remove it, but the risk rises sharply when kidney function is reduced, so anyone with a kidney problem needs advice first. Anyone pregnant or breastfeeding, or taking prescribed tablets, should speak to a GP or pharmacist first.

Sources: NIH Office of Dietary Supplements; Mayo Clinic Press; peer-reviewed trial, Nature and Science of Sleep, 2025.

Magnesium bisglycinate capsules are for people who want a gentle form of magnesium for daily use. That includes people whose stomach objected to other forms, and people who take magnesium in the evening. One capsule covers just over a third of the daily reference value, so it suits anyone topping up a diet that already contains green vegetables, nuts, wholegrains and beans rather than replacing it. Anyone who wants a pure chelate without oxide should read the ingredient line before choosing this one.

Sources: Food Standards Scotland; NIH Office of Dietary Supplements; product label.