Health Reference LibraryMagnesium bisglycinate vs magnesium glycinate: is there a difference?
This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.
Summary
There is no difference. Magnesium bisglycinate and magnesium glycinate are two names for one compound, a magnesium atom bound to two glycine molecules. Chemists and most UK labels say bisglycinate, because there are two glycines; American brands and most search boxes say glycinate. When you compare products, the name tells you nothing, so read three things instead: the amount of elemental magnesium per capsule, whether a second form such as oxide has been added to reach that amount, and how many capsules a day the label asks for. Bisglycinate on its own is bulky, so many capsules add oxide to lift the dose, and honest labels say so.
How it works
The glycine part is why people choose this form. The bound glycine is thought to be carried across the gut wall by amino acid transport as well as by the usual magnesium routes, and glycine itself is a calming amino acid in the nervous system, which is where the reputation for evening use comes from. The 1994 comparison in people with bowel resections found magnesium diglycinate better absorbed than oxide, and the 2021 systematic review of magnesium supplements places organic forms such as glycinate and citrate ahead of oxide for bioavailability. The head to head trials between glycinate and citrate do not exist, so claims that one beats the other rest on their different side effect profiles rather than absorption data.
Effective dose
The UK reference intake is 300 mg of magnesium a day for men and 270 mg for women aged 19 to 64, from food and supplements together. The NHS notes that more than 400 mg a day from supplements can loosen the bowels in the short term, though bisglycinate is the form least likely to do that. Trials of magnesium for sleep and stress used 250 to 500 mg of elemental magnesium a day for six to eight weeks. Count the elemental figure on the label, not the compound weight; 1000 mg of magnesium bisglycinate is roughly 140 mg of magnesium.
Forms compared
The chemistry settles the argument. Glycine is the smallest amino acid, and one magnesium atom carries two of them, which is what the prefix bis means. Bisglycinate is the technically correct name; glycinate is the shorthand that stuck. Some products write chelated magnesium, magnesium chelate or magnesium diglycinate, and those are the same thing again. What genuinely varies between products is the dose of elemental magnesium, because the compound is only about one seventh magnesium by weight, and whether the manufacturer has blended in magnesium oxide to reach a useful figure in one capsule. A capsule labelled 100 mg magnesium as bisglycinate alone would be very large, so a blend is common and not a fault as long as the label says so.
Timing
Bisglycinate suits the evening. Take it with or after your last meal, or an hour before bed if you are using it for sleep. Food does not block absorption and reduces the chance of an unsettled stomach. If the label asks for two or three capsules, splitting them across the day is fine and may be better absorbed than one large dose.
Safety profile
Bisglycinate is the form with the fewest bowel complaints because the glycine bond keeps the magnesium from acting as an osmotic laxative in the way oxide and citrate can. Anyone with reduced kidney function should not take magnesium supplements without their GP, because the kidneys clear the excess. Very high intakes cause low blood pressure, drowsiness and muscle weakness; those are the signs to stop and seek advice.
Guideline positions
UK reference intakes for magnesium: 300 mg a day for men and 270 mg for women (NHS). NIH Office of Dietary Supplements: supplemental upper level of 350 mg a day for adults, set by the bowel effect. Bioavailability of magnesium food supplements: systematic review (2021). Magnesium diglycinate versus oxide absorption study (1994).
Practical framework
If you searched for either name, you are looking for the same thing, so buy on the elemental figure and the honesty of the label. Nutri Tailor stocks [magnesium bisglycinate capsules](/products/magnesium-bisglycinate) at 133 mg of elemental magnesium per capsule, bisglycinate blended with oxide to reach that dose, made in the UK. For a daytime form that also helps a sluggish bowel, see magnesium glycinate vs magnesium citrate, and for the whole shelf, which magnesium is best. This is a summary of published research, not personal health advice. Talk to your GP or a registered nutritional therapist before changing what you take, especially if you are pregnant, have a diagnosed condition or are under ongoing care.
Common misconceptions
That bisglycinate is a stronger or purer version of glycinate: it is the same molecule. That the glycinate name means the product contains no oxide: many do, and only the label will tell you. That 400 mg on the front of a bottle means 400 mg of magnesium: it often means 400 mg of the compound, which is closer to 55 mg of magnesium.
Forms compared
| Magnesium Bisglycinate | Magnesium Glycinate | |
|---|---|---|
Sources
- Pardo MR, Garicano Vilar E, San Mauro Martín I, Camina Martín MA 2021. Bioavailability of magnesium food supplements: A systematic review. Nutrition. PMID: 34111673 · DOI: 10.1016/j.nut.2021.111294
- Schuette SA, Lashner BA, Janghorbani M 1994. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. Journal of Parenteral and Enteral Nutrition. PMID: 7815675 · DOI: 10.1177/0148607194018005430
- NIH Office of Dietary Supplements. NIH Office of Dietary Supplements — Magnesium Fact Sheet for Health Professionals. NIH Office of Dietary Supplements (US government).
- Macian N et al 2022. Short-Term Magnesium Therapy Alleviates Moderate Stress in Patients with Fibromyalgia: A Randomized Double-Blind Clinical Trial. Nutrients. PMID: 35631229 · DOI: 10.3390/nu14102088