How much magnesium glycinate should you take?
The short answer
Recent trials of magnesium glycinate have used around 250 mg of elemental magnesium a day, and the NHS says keeping the total from all supplements at 400 mg or less is unlikely to cause harm.
The right amount for you depends on how much magnesium you already get from food, why you are taking it and how your digestion responds. Below we explain the official guidance, the doses used in research and how to read a label without getting caught out.
How much magnesium do adults need each day?
The NHS says men aged 19 to 64 need 300 mg of magnesium a day and women aged 19 to 64 need 270 mg.
That figure is your total need from all sources, including food. Leafy green vegetables, nuts, seeds and wholegrains are good sources, so many people get a fair share from their diet already. A supplement is there to top up, not to replace food.
| Guide | Amount | Source |
|---|---|---|
| Daily need, men 19 to 64 | 300 mg | NHS |
| Daily need, women 19 to 64 | 270 mg | NHS |
| Supplements unlikely to cause harm | 400 mg a day or less | NHS |
| Upper limit from supplements, adults | 350 mg a day | NIH (US) |
| Dose used in a 2025 sleep trial | 250 mg elemental magnesium as bisglycinate | Schuster et al. |
What is the maximum safe amount of magnesium glycinate?
In the UK, the NHS says taking 400 mg a day or less of magnesium from supplements is unlikely to cause any harm.
The US National Institutes of Health sets a more cautious upper limit of 350 mg a day from supplements and medicines for adults. That limit does not include magnesium from food, and it is based mainly on the risk of diarrhoea. If you want to stay well within both, aim for 350 mg or less from supplements.
Taking more than 400 mg over a short time can cause diarrhoea. Very high intakes from supplements or medicines can cause more serious problems, which is why it pays to add up every product you take.
Elemental magnesium vs total compound: read the label
The number that matters is elemental magnesium, not the weight of the magnesium glycinate compound.
Magnesium glycinate is magnesium bound to the amino acid glycine. The glycine adds weight, so a capsule containing a large amount of magnesium glycinate delivers much less actual magnesium. Good labels state both. If a label only gives the compound weight, it is hard to know what dose you are taking.
Blended products, which combine glycinate with forms such as malate or aspartate, should list the total elemental magnesium per serving. Use that figure when you compare products or add up your daily intake.
What doses have been used in research?
Recent trials have used doses in the region of 250 to 300 mg of elemental magnesium a day.
- Sleep: a 2025 randomised trial gave 155 adults with poor sleep 250 mg of elemental magnesium as bisglycinate daily for four weeks. Insomnia scores improved a little more than with placebo, and people with low dietary magnesium seemed to benefit most.
- Absorption: a 2003 trial gave healthy adults 300 mg of magnesium a day for 60 days to compare forms.
- Wider reviews: a 2024 systematic review of magnesium for sleep and anxiety found doses, forms and study lengths varied widely. Most studies used magnesium oxide, and side effects were generally mild, mainly loose stools.
These doses sit within the NHS guide, which is reassuring. They do not mean more is better.
When is the best time to take magnesium glycinate?
There is no proven best time, so choose a time you can stick to each day.
Many people take magnesium glycinate in the evening as part of a wind-down routine. Others split the dose between morning and evening, which some find easier on the stomach. Consistency matters more than the clock, because studies measure effects over weeks.
If you take medicines that interact with magnesium, timing matters more. Magnesium can reduce how well bisphosphonates and some antibiotics are absorbed if they are taken too close together, so ask your pharmacist how far apart to space them.
What does magnesium do in the body?
Magnesium is involved in hundreds of everyday processes, from energy to muscles to the nervous system.
The authorised health claims for magnesium in Great Britain say it contributes to:
- a reduction of tiredness and fatigue
- normal energy-yielding metabolism
- normal functioning of the nervous system
- normal psychological function
- normal muscle function
- the maintenance of normal bones and teeth
Signs you are taking too much
The most common sign of too much magnesium from supplements is diarrhoea, often with nausea or stomach cramps.
If this happens, reduce your dose or stop and see whether it settles. Magnesium glycinate is usually gentler than some other forms, but any magnesium can loosen stools at high amounts.
Who should check with a GP or pharmacist first?
Speak to your GP or pharmacist before taking magnesium glycinate if any of these apply to you.
- Kidney disease: reduced kidney function makes it harder to clear excess magnesium, which raises the risk of build-up.
- Regular medicines: including bisphosphonates for bone health, some antibiotics, diuretics and long-term proton pump inhibitors for acid reflux.
- Pregnancy or breastfeeding: check with your midwife, GP or pharmacist first.
- Children: adult doses are not suitable for children.
Our approach
A simple, well-absorbed daily magnesium, taken consistently, is a good place to start.
Perfect Blend Magnesium leads with magnesium bisglycinate, alongside magnesium malate and aspartate, zinc, vitamin D3 and purified shilajit. Follow the serving size on the label, count any other magnesium you take, and you will stay comfortably within the guidance. You can explore related formulas in our sleep collection.