In short: Magnesium glycinate and magnesium bisglycinate are the same compound: magnesium bound to two molecules of the amino acid glycine. This form is considered well tolerated, is absorbed better than magnesium oxide in studies and is a good fit for the evening: in one study, sleep problems decreased more with it than with a placebo. Whether a supplement has been bulked out with cheaper magnesium oxide is revealed by one number on the pack.
Key points
- Same substance, two names: in the shops, "glycinate" and "bisglycinate" refer to the same compound.
- Well tolerated: in one study, glycinate was better tolerated than magnesium oxide. Loose stools are possible, mainly with large amounts taken at once.
- Absorption: organic forms such as glycinate are absorbed better than magnesium oxide, best of all in several smaller doses.
- Sleep: in a study of 155 adults, sleep problems decreased more with bisglycinate than with a placebo.
- Check it's genuine: pure magnesium bisglycinate contains no more than 14.1% magnesium. If the pack states more, something else has been added.
Contents
- What is magnesium glycinate?
- Magnesium glycinate vs bisglycinate: what is the difference?
- Is it better absorbed than citrate or oxide?
- Benefits: what do studies show?
- What are the side effects of magnesium glycinate?
- Genuine or bulked out? How to check a supplement
- How and when should you take magnesium glycinate?
- Frequently asked questions
- Limits of the research and all sources
What is magnesium glycinate?
Magnesium glycinate is magnesium that is firmly bound to the amino acid glycine. Glycine is the smallest amino acid and is found in almost every protein you eat.
The magnesium isn't loosely attached; it is held from both sides, with each glycine molecule gripping it with two arms. Chemists call this kind of bond a chelate (from the Greek word for a crab's claw). The result is a white powder that dissolves well in water.
What the studies show: Structural analyses confirm that in this compound, magnesium is bound via the amino group and the acid group of glycine, forming two small rings.1
Magnesium glycinate vs bisglycinate: what is the difference?
In the shops, there is none. Both names stand for the same compound of one magnesium and two glycine. The prefix "bis" simply counts: two glycine. "Magnesium glycinate" is the short form, "magnesium bisglycinate" the more precise name.
There is a real difference, though. It just lies in the product, not in the name:
| What's inside | Magnesium content | How to spot it |
|---|---|---|
| Pure magnesium bisglycinate | no more than 14.1% | the figure on the pack fits the calculation below |
| "Buffered" glycinate (mixed with magnesium oxide) | well above 14.1% | more magnesium per gram than is chemically possible |
| Loose mixture of glycine and magnesium oxide | any amount | no genuine bond detectable in the lab |
"Buffered" sounds like a mark of quality, but it usually means that part of the magnesium comes from magnesium oxide. That isn't prohibited and it isn't harmful. It just means you aren't buying what it says on the front.
What the studies show: "Buffered" bisglycinate (with magnesium oxide) has already been tested as a separate variant in cell experiments. It came out slightly below pure bisglycinate, but the difference was not statistically reliable.2 A lab analysis of 22 food supplements found that two magnesium products did not contain the declared magnesium compound at all.3
Is magnesium glycinate better absorbed than citrate or oxide?
Compared with magnesium oxide, yes. Like citrate, glycinate is one of the organic forms that your body absorbs better. You get the most out of it if you take it in smaller doses and choose a supplement that dissolves well in your stomach.
What the studies show: A systematic review of 14 comparative studies concludes that organic forms such as citrate or glycinate are absorbed better than inorganic forms such as oxide, and that the share absorbed falls as the amount goes up.4 In patients who had undergone bowel surgery, the four with the poorest absorption took up twice as much magnesium from the glycinate chelate as from magnesium oxide (23.5% vs 11.8%).5
The supplement itself matters too: when 15 commercially available supplements were compared in the lab, they dissolved to very different degrees. The worst of them was also absorbed markedly less well in people.8
Our take: Like citrate, glycinate is one of the well-absorbed organic forms, and it is also considered particularly gentle on the stomach. If you have a sensitive stomach or want to take magnesium in the evening, glycinate is a good choice. For your magnesium supply, what matters most is that you take an honestly labelled supplement regularly and in sensible amounts. How glycinate and citrate compare head-to-head over several weeks is something longer studies have yet to show.
Magnesium glycinate benefits: what do studies show?
In the EU, four officially authorised statements about magnesium are relevant here. They apply to every form, including glycinate:
- Magnesium contributes to normal functioning of the nervous system.
- Magnesium contributes to normal psychological function.
- Magnesium contributes to normal muscle function.
- Magnesium contributes to a reduction of tiredness and fatigue.
The question people ask most about glycinate specifically is whether it helps you sleep. There is a dedicated controlled study on this, with an encouraging result.
What the studies show: In a German study, 155 adults who slept poorly took 250 mg of magnesium as bisglycinate or a dummy pill for four weeks. Sleep problems decreased more with bisglycinate than with the dummy pill. The effect was most pronounced in people who got little magnesium from their diet.9
Then there is the glycine itself. In small studies of people who slept poorly, 3 g of glycine before bed improved how well they felt they had slept.10, 11 In one of them, participants also reached deep sleep faster.10 For comparison: 250 mg of magnesium as bisglycinate provides around 1.5 g of glycine, roughly half the amount used in these studies (our calculation from the molar masses).
Our take: Bisglycinate has its own controlled sleep study with a positive result, and the glycine it contains also improved sleep quality in studies. If you want to wind down better in the evening, glycinate is a good choice to take with your evening meal, especially if you get little magnesium from your diet. How much the glycine contributes to the effect is something further studies have yet to show.
There are also early indications regarding stress: in rats, glycinate led to less anxious behaviour.12
What are the side effects of magnesium glycinate?
Glycinate is considered well tolerated; in one study it was better tolerated than magnesium oxide. If side effects do occur, they are usually loose stools or diarrhoea, and only with larger amounts taken at once. Less often, there is a feeling of pressure in the stomach.
Why diarrhoea? Magnesium that isn't absorbed in the gut draws in water. That's why splitting the amount into two doses and taking it with food almost always helps.
What the studies show: The European Food Safety Authority (EFSA) sets the upper limit for magnesium from supplements at 250 mg a day, precisely because of possible digestive complaints.13 In the study of patients after bowel surgery, all participants tolerated the glycinate chelate better than magnesium oxide.5 An analysis of more recent studies found no difference in diarrhoea between magnesium and placebo in most cases, even at amounts above the upper limit.14
Important: If your kidney function is reduced, magnesium can build up in the body.15 In that case, talk to your GP first. With thyroid hormone, certain antibiotics and osteoporosis medicines, you need to leave a gap of a few hours. You'll find the details in our article When should you take magnesium?
Genuine or bulked out? How to check a supplement
The good news: you don't need a lab to spot the worst cases. One number that almost every pack states is enough.
Pure magnesium bisglycinate is at most 14.1% magnesium. This follows from the weight of the atoms: magnesium weighs 24.3 units, the whole compound 172.4.16 Pure bisglycinate cannot contain more magnesium than that. If the powder still contains water, the share is even lower.
How to do it: Look for two figures per serving on the pack: the amount of magnesium bisglycinate and the amount of magnesium. Divide the magnesium by the bisglycinate.
- 1,000 mg bisglycinate with 140 mg magnesium = 14% → consistent with pure bisglycinate.
- 1,000 mg bisglycinate with 200 mg magnesium = 20% → chemically impossible for pure bisglycinate. Another form of magnesium has been added, usually oxide.
If only the amount of magnesium is given, but not how much bisglycinate, you can't do the calculation. That in itself is a reason to ask the manufacturer for more details.
The calculation has its limits: it only shows whether there is too much magnesium. Whether the magnesium is actually bound or has simply been mixed loosely with glycine can only be seen in the lab, for example with X-ray diffraction (XRD) or infrared spectroscopy.1 It was X-ray diffraction that researchers used when they failed to find the declared magnesium compound in two of 22 products tested.3
Tip: If you want to know more precisely, our bisglycinate authenticity check does the maths on the figures from your pack. A rough test at home: open a capsule and stir the powder into a glass of water. Pure bisglycinate dissolves well; magnesium oxide barely dissolves and settles at the bottom. This isn't proof, because fillers can settle too.
How and when should you take magnesium glycinate?
Take it with a meal and, from supplements, stick to no more than 250 mg of magnesium a day unless your doctor advises otherwise. If you take more than about 250 mg, it's best to split it between two meals. The time of day is secondary. If you're taking it for sleep, simply take it with your evening meal.
One thing to watch when reading the pack: the amounts refer to the magnesium, not the bisglycinate. 1,000 mg of bisglycinate contains only around 140 mg of magnesium.
What the studies show: The sleep study used 250 mg of magnesium a day as bisglycinate.9 We've summarised how dose, timing and meals affect things in When should you take magnesium? How much magnesium you need in total is covered in How much magnesium per day?
Frequently asked questions
Is magnesium glycinate the same as magnesium bisglycinate? Yes. Both names stand for magnesium bound to two glycine. Differences only arise from what else goes into the product, such as magnesium oxide in "buffered" supplements.
What is magnesium glycinate good for? The same things magnesium in general is good for. Magnesium contributes to a reduction of tiredness and fatigue. Magnesium contributes to normal muscle function. Magnesium contributes to normal psychological function. For bisglycinate specifically, there is also a study on sleep with a positive result.9
Does magnesium glycinate make you tired? If anything, the opposite: the sleep study looked at better sleep at night, not at tiredness during the day.9 Magnesium contributes to a reduction of tiredness and fatigue.
Magnesium glycinate vs citrate: which is better? Both are among the well-absorbed forms and do better than magnesium oxide.4 Glycinate is also considered particularly gentle on the stomach and, thanks to the sleep study, is popular for the evening.9 You'll find a comparison of all forms in Which magnesium is best?
Is 500 mg of magnesium glycinate too much? That depends on what the 500 mg refers to. If it means 500 mg of the compound magnesium bisglycinate, that is at most about 70 mg of magnesium (14.1%, our calculation). If it means 500 mg of magnesium, that is twice the upper limit of 250 mg a day for magnesium from supplements. In that case, talk to your GP first.
Does magnesium glycinate help with stress? Magnesium contributes to normal psychological function. Magnesium contributes to normal functioning of the nervous system. For glycinate specifically, there are early indications from animal studies: rats showed less anxious behaviour with it.12
How long can you take magnesium glycinate for? Up to 250 mg of magnesium a day from supplements, there is no time limit.13 This does not apply if you have kidney disease; in that case, only after talking to your doctor.15
Is magnesium glycinate vegan? That depends on the product. What matters is where the glycine comes from and, above all, the capsule shell: capsules made from plant cellulose (HPMC) are vegan, gelatine capsules are not. Look for a vegan label.
Limits of the research and all sources
So far there are few human studies on the glycinate form, and most comparisons measure blood levels after a single dose. That says little about your magnesium status over weeks, because blood levels are tightly regulated. How glycinate compares directly with citrate is an open question. In a study of 40 healthy people, blood magnesium did not rise measurably after a single dose of bisglycinate, whereas it did after citrate and oxide.6 Another study found less magnesium in red blood cells with bisglycinate than with a newly developed competing form.7 Both studies were funded by manufacturers of these competing forms. We found no direct comparisons of tolerability with citrate.
In the study of patients after bowel surgery, the advantage only appeared in the patients with poor absorption; across the whole group, there was no difference.5 In the sleep study, symptoms also improved with the placebo, and the additional effect of bisglycinate was small.9 Whether the glycine contributes in this combination was not specifically studied. For stress, there are only animal studies so far.12
Show all 16 sources
| # | Study | Who was studied | Result | Strength of evidence |
|---|---|---|---|---|
| 1 | Yin et al. 2017, J Innov Opt Health Sci | lab analysis of glycinate compounds | magnesium bound via amino and acid group, two rings | structural analysis |
| 2 | Hartle et al. 2016, FASEB J | intestinal cells in the lab, 5 forms | bisglycinate highest, buffered slightly lower, citrate and oxide lower | cell study |
| 3 | Jendrzejewska 2020, Front Chem | 22 food supplements, X-ray diffraction | declared compound not found in 2 magnesium products | lab analysis |
| 4 | Pardo et al. 2021, Nutrition | 14 comparative studies | organic forms better than inorganic, share absorbed falls with amount | systematic review |
| 5 | Schuette et al. 1994, JPEN | 12 patients after bowel surgery, 100 mg | no difference overall; with poor absorption 23.5% vs 11.8%; better tolerated | small controlled study |
| 6 | Pajuelo et al. 2024, Nutrients | 40 healthy people, one dose each | no measurable rise in blood after bisglycinate | controlled study, funded by maker of a competing form |
| 7 | Brilli et al. 2018, Eur Rev Med Pharmacol Sci | healthy people, 350 mg each | advantage for competing form in red blood cells | controlled study, funded by maker of a competing form |
| 8 | Blancquaert et al. 2019, Nutrients | 15 supplements in the lab, 30 people | dissolution and absorption varied widely between products | lab + small study |
| 9 | Schuster et al. 2025, Nat Sci Sleep | 155 adults, 250 mg bisglycinate, 4 weeks | sleep problems reduced more than with placebo (small effect) | controlled study |
| 10 | Yamadera et al. 2007, Sleep Biol Rhythms | adults with poor sleep, 3 g glycine | better sleep quality, reached deep sleep faster | small controlled study |
| 11 | Inagawa et al. 2006, Sleep Biol Rhythms | adults with poor sleep, 3 g glycine | fresher and clearer-headed in the morning | small controlled study |
| 12 | Koc et al. 2025, Biol Trace Elem Res | 38 rats, 8 weeks | glycinate: less anxious behaviour | animal study |
| 13 | EFSA / SCF 2001 | official scientific opinion | upper limit 250 mg/day from supplements | official assessment |
| 14 | Costello et al. 2023, Adv Nutr | 10 studies since 1997 | mostly no difference in diarrhoea compared with placebo | review with commentary |
| 15 | Rosner et al. 2023, Mayo Clin Proc | review article | build-up with reduced kidney function | review |
| 16 | PubChem CID 84645 | chemical database | molar mass of magnesium bisglycinate 172.42 g/mol → 14.1% magnesium | reference data |
Author: PRONESIUM Editorial Team · Last reviewed: 29/09/2026 · This article does not replace medical advice.
