Magnesium glycinate is one of the best absorbed and gentlest forms of magnesium, so if you are going to supplement, it is a sensible pick. The fuller answer: most people in the UK get enough magnesium from food, and the evidence that any form reliably improves sleep or stops cramps in well-nourished people is modest at best.
What magnesium does
Magnesium is involved in hundreds of processes, including muscle and nerve function, energy production and bone structure. It is found widely in food: nuts, seeds, wholegrains, beans, leafy greens and dark chocolate all supply useful amounts, so a reasonably varied diet usually covers it. A handful of almonds, a serving of cooked spinach or a portion of wholegrain cereal each make a meaningful contribution. True deficiency is uncommon in otherwise healthy people eating normally.
UK adults need around 300mg of magnesium a day for men and 270mg for women, and food should supply most of that. If you are weighing up whether you need a supplement at all, diet is the sensible starting point.
Magnesium glycinate vs citrate vs oxide
This is where the confusion lives. Magnesium is always bound to something else, and that partner affects how well it is absorbed and how it behaves:
- Magnesium oxide: cheap and common, but poorly absorbed. More of it passes through the gut, which is why it is also used as a laxative.
- Magnesium citrate: better absorbed than oxide, reasonably priced, though it can loosen stools at higher doses.
- Magnesium glycinate (bisglycinate): well absorbed and gentle on the stomach, often marketed for sleep and relaxation.
- Other forms, including malate, taurate and threonate, are sold with specific claims that generally run ahead of the human evidence.
One naming point worth clearing up: magnesium glycinate and magnesium bisglycinate are the same compound, magnesium bound to two molecules of the amino acid glycine. Brands use the two names interchangeably, so there is no reason to pay more for one over the other.
The practical takeaway: if you are going to supplement, a well-absorbed form like citrate or glycinate makes more sense than oxide, even though oxide lists a bigger number on the front because it contains more elemental magnesium by weight. This is a common trick worth spotting: a high headline dose of a poorly absorbed form can deliver less usable magnesium than a smaller dose of a better one. Our guide to reading supplement labels explains how to check the elemental dose.
You will also see magnesium in effervescent tablets, sprays and bath salts. Skin absorption from sprays and Epsom-salt baths is often claimed but poorly supported by evidence, so if you want a reliable dose, an oral supplement is the sensible route.
What is magnesium glycinate good for?
Magnesium glycinate is usually marketed for sleep, relaxation and muscle recovery, and it is the form most often suggested for people whose stomachs are unsettled by citrate or oxide. The glycine it is bound to is itself a calming neurotransmitter, which is part of the marketing story, though human evidence that this makes a practical difference is thin.
In the UK, magnesium glycinate typically costs more than citrate or oxide. That premium buys better tolerability rather than better results. If sleep is your main interest, we look at that evidence in detail in our article on magnesium for sleep.
The sleep and cramp evidence
Magnesium is heavily marketed for sleep. The honest picture: observational research links higher magnesium intake with slightly better sleep quality, but trial evidence is limited, largely low-quality, and strongest in people who were actually deficient to begin with. For a well-nourished adult sleeping poorly, magnesium glycinate is unlikely to be the answer, and general sleep habits matter far more.
It is a similar story for muscle cramps, including the night cramps common in older adults and pregnancy. A Cochrane review found little convincing benefit from magnesium for cramps in the general population, despite its popularity for this use.
How much magnesium glycinate should I take?
There is no special dose for magnesium glycinate: what matters is the elemental magnesium each capsule delivers, which is listed on the label. The NHS advises that taking 400mg or less a day of magnesium from supplements is unlikely to cause harm. Above that, loose stools become common, and people with kidney problems should avoid high doses altogether.
Detailed safety reviews, such as the NIH Office of Dietary Supplements fact sheet, reach a similar conclusion: modest supplemental doses are well tolerated, and gut side effects are the main limit. Magnesium glycinate side effects are uncommon at sensible doses; loose stools are the most likely across all forms.
When to take magnesium glycinate matters less than the marketing suggests. Absorption is similar at any time of day, so take it with food if it unsettles your stomach, and if you are using it as part of a wind-down routine, an hour before bed is a reasonable habit. Consistency matters more than clock time.
Who is more likely to run low
Some groups genuinely are at higher risk of low magnesium and may benefit from attention, ideally with GP input:
- People who drink heavily, as alcohol increases magnesium loss.
- People with conditions affecting absorption, such as some gut disorders.
- People on long-term medicines that lower magnesium, including some diuretics and proton pump inhibitors.
- Those with poorly controlled diabetes.
If you take regular medication, it is worth checking our guide to supplements that interact with medicines before adding magnesium, as it can affect the absorption of some antibiotics and other drugs.
The honest bottom line
For most people, food covers magnesium and a supplement is optional. If you want to try one, whether for cramps, sleep or general reassurance, choose citrate or magnesium glycinate, keep the dose sensible, and be aware that supplemental magnesium can cause loose stools. Very high doses should be avoided unless a clinician advises, particularly if you have kidney problems. For where it fits with other supplements, see supplement timing.
