Health Reference LibraryWhat is magnesium bisglycinate and when is it the right form?
This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.
Summary
Magnesium bisglycinate and magnesium glycinate are the same compound, magnesium bound to two glycine molecules. Absorption evidence is more even than marketing suggests. The chelate matched oxide overall in a randomised crossover trial, with a clear advantage only in the most impaired absorbers, while citrate performed at least as well as a chelate in a 60 day healthy adult comparison. The real case for bisglycinate is gut comfort, since the chelate avoids the laxative effect that makes other forms hard to take daily. Typical doses are 100 to 300 mg elemental a day, within the NHS 400 mg supplemental caution.
How it works
In bisglycinate the magnesium ion is chelated between two glycine molecules. Part of the dose appears to be absorbed intact through a dipeptide transport route in the proximal small intestine, which sidesteps some of the competition and saturation that affects free magnesium ion absorption. Glycine itself is a calming inhibitory neurotransmitter, which is one reason the form is popular for evening use, though the sleep evidence for magnesium rests on magnesium status rather than the glycine carrier.
Effective dose
Typical supplemental doses are 100 to 300 mg of elemental magnesium a day, against UK reference intakes of 300 mg for men and 270 mg for women aged 19 to 64 from all sources. Read the elemental figure on the label rather than the compound weight, since the glycine carrier accounts for most of the compound mass. NHS guidance cautions that more than 400 mg a day from supplements short term commonly causes diarrhoea, though bisglycinate is the form least likely to.
Forms compared
Fully reacted bisglycinate contains a relatively low proportion of elemental magnesium, which is the trade for its gentleness, and some cheaper products buffer bisglycinate with oxide to raise the elemental number, which reintroduces the tolerability problem. A product labelled fully reacted or fully chelated is the cleaner choice. The dedicated citrate entry and the form comparison guides on this site cover the alternatives.
Timing
Evening dosing is the common pattern where sleep support is the aim, and bisglycinate's gentleness makes it practical on an empty stomach for many people, though taking magnesium with food remains the default advice. The timing entry on this site covers morning versus night in full.
Safety profile
Oral magnesium at these doses has a wide safety margin in people with normal kidney function. Anyone with reduced kidney function should not supplement without GP advice. Loose stools are the main dose limiting effect across magnesium forms and are least likely with bisglycinate. Persistent symptoms that prompted supplementation in the first place, such as cramps or palpitations, deserve a GP conversation rather than escalating doses.
Special populations
Gentleness makes bisglycinate a common choice for older adults and for people with sensitive digestion or a history of loose stools on citrate or oxide. The randomised evidence for the chelate advantage is strongest in people with impaired absorption, such as after gut surgery, which is precisely the group who should be supplementing under GP guidance anyway. Pregnancy has its own entry on this site.
Interactions
Magnesium can reduce absorption of tetracycline and quinolone antibiotics and of bisphosphonates taken at the same time, so doses are usually separated by several hours. Long term proton pump inhibitor use and some diuretics lower magnesium, which can be a reason a GP suggests supplementing. A pharmacist can check spacing against regular prescriptions.
Guideline positions
UK reference nutrient intakes are 300 mg a day for men and 270 mg for women aged 19 to 64, with the NHS 400 mg a day short term supplemental caution. No UK guideline recommends one magnesium form over another, which is why the trial evidence and tolerability carry the decision.
Practical framework
A workable order. First, decide whether magnesium is warranted at all, which the symptoms and testing entries on this site cover, and which a GP conversation settles where symptoms persist. Second, choose the form on tolerability. If citrate or oxide has caused loose stools, or gentleness matters more than pence per milligram, bisglycinate is the natural pick, available as fully reacted magnesium bisglycinate at nutritailor.co.uk/products/magnesium-bisglycinate. Third, dose at 100 to 300 mg elemental a day with food, evening if sleep is the aim. Fourth, judge the result over weeks, not days, and the sleep timeline entry sets those expectations honestly.
Common misconceptions
Claim, glycinate and bisglycinate are different products. They are the same compound under two names, and bis simply counts the two glycine molecules. Claim, bisglycinate is proven the best absorbed form. The randomised evidence shows the chelate matching oxide overall in one trial with an advantage only in impaired absorbers, and citrate performing at least as well as a chelate in another, so tolerability rather than superior absorption is the honest case. Claim, a high milligram number on the front label means a strong product. The elemental magnesium figure is what counts, and buffered products using oxide to inflate the number trade away the gentleness that justified the form.
Sources
- Schuette SA, Lashner BA, Janghorbani M 1994. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN J Parenter Enteral Nutr 18(5):430-435.
- Walker AF et al 2003. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research 16:183.
- NHS 2024. NHS vitamins and minerals (others) page. NHS.
- NIH Office of Dietary Supplements 2022. Magnesium Fact Sheet for Health Professionals. National Institutes of Health.