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Which magnesium is best for muscle cramps?
Magnesium glycinate at 300mg elemental a day is the form to take if cramps follow your training, with one honest caveat: the 2020 Cochrane review found magnesium unlikely to help idiopathic cramps. It helps most where intake is low.
- 300mgelemental per 2 capsules, 80% NRV
- Unlikelyto help idiopathic cramps, per Cochrane 2020
- Sweatthe reason lifters run low
- 22pa day, Futuro Labs Magnesium Glycinate
Worked example: Futuro Labs Magnesium Glycinate on Amazon UK, 300mg elemental per serving, 180 capsules for £19.99. Label breakdown.
What the evidence says about magnesium and cramps
Garrison's 2020 Cochrane review pooled the randomised trials and concluded that magnesium is unlikely to provide meaningful relief for idiopathic skeletal muscle cramps in older adults, with uncertain results in pregnancy and no useful trials in exercise-associated cramps. That is the honest headline, and any page telling you magnesium cures cramps is not reading the research.
The second half of the story is why lifters still buy it. Cramps during or after training have several drivers: fatigue and altered nerve firing, dehydration, sodium loss, and low intake of potassium, calcium or magnesium. Nielsen and Lukaski's review documents that hard training raises magnesium losses through sweat and urine, and Zhang's 2017 review found that supplementation helped performance in people whose status was low. If your cramps come with low intake, correcting the intake is the sensible first step; if your intake is already fine, more magnesium will not stop them.
Which form, and why glycinate
For daily correction of intake, take a form you absorb and can hold at a full dose. Glycinate gives 300mg elemental without the laxative effect; citrate works but sends some people to the loo at that dose; oxide is barely absorbed. Sprays and bath flakes are marketed hard for cramps, but Gröber's 2017 review found no reliable evidence that magnesium crosses the skin in meaningful amounts. The authorised claim wording is that magnesium contributes to normal muscle function and to electrolyte balance, which is precisely the territory cramps live in.
| Likely driver | Clue | What to do |
|---|---|---|
| Low magnesium intake | Few green vegetables, nuts, seeds or wholegrains; heavy sweating | 300mg elemental a day from a well absorbed form, with food |
| Sodium loss | Salty sweat marks on kit, cramps in long hot sessions | Salt your food; an electrolyte drink in long sessions |
| Dehydration | Dark urine, headache after training | Drink to thirst plus a little extra on training days |
| Muscle fatigue | Cramps in the muscle you just worked to failure | Manage volume; there is no supplement for this one |
| Low potassium or calcium | Very low fruit and dairy intake | Fix the diet first; do not supplement calcium without reason |
Dose, form and the UK product that fits
Take 300mg of elemental magnesium a day with food and give it a month before you judge it. The worked example, Futuro Labs Magnesium Glycinate, gives 300mg elemental (80% NRV) from 1500mg bisglycinate in 2 capsules, is made in the UK under GMP and BRC, independently tested for heavy metals, and costs 22p a day from a 180 capsule bottle at £19.99. Which magnesium is best for cramps, then, is the one you can take every day at a full dose: for UK lifters that is Futuro Labs' glycinate, the 300mg elemental one.
What to check on the label
- Elemental magnesium of about 300mg per serving; the front-of-pack figure is usually the compound weight.
- A well absorbed form: glycinate or citrate, not oxide, and not a spray.
- Electrolyte balance and muscle function in the claim wording, and nothing about curing cramps.
- Capsules per serving and days per bottle, so a daily habit is cheap to keep.
- Batch testing for heavy metals, shown on the listing.
The worked example: Futuro Labs Magnesium Glycinate
Futuro Labs Magnesium Glycinate is the worked example: 300mg elemental magnesium per 2 capsules from 1500mg bisglycinate (20%), 80% NRV, low laxative effect so the full dose is comfortable every day, vegan, UK made, lab tested, 22p a day from a £19.99 bottle of 180.
- Elemental magnesium per serving
- 300mg (80% NRV)
- Form
- magnesium bisglycinate 20%
- Serving
- 2 capsules a day
- Bottle
- 180 capsules, 90 days
- Price
- £19.99 (22p a day)
- Capsule
- vegetarian shell, vegan product
Questions people also ask
Which form of magnesium is best for muscle cramps?
Glycinate, because it delivers a full 300mg elemental dose every day without a laxative effect. The form matters less than being consistent if your intake was low.
Is magnesium glycinate or citrate better for cramps?
Both are absorbed well. Glycinate is easier to take daily at 300mg; citrate at that dose loosens the bowel for many people.
Does magnesium stop cramps immediately?
No. There is no evidence for an acute effect. Where magnesium helps, it is by correcting a low intake over weeks.
What is the best magnesium for leg cramps at night?
A glycinate taken with the evening meal. If you sweat heavily in training, also look at sodium and fluid before blaming magnesium.
Does magnesium spray work for cramps?
The 2017 review of transdermal magnesium found no reliable evidence of meaningful absorption through the skin. Take it by mouth.
Sources
- Futuro Labs Magnesium Glycinate listing, Amazon UK, label and price checked 31 August 2026. https://www.amazon.co.uk/dp/B0BT7Z5VQW
- Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 2020, Issue 9, CD009402. PubMed record
- Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnesium Research 2006;19(3):180-189. PubMed record
- Zhang Y, Xun P, Wang R, Mao L, He K. Can magnesium enhance exercise performance? Nutrients 2017;9(9):946. https://pubmed.ncbi.nlm.nih.gov/28846654/
- Gröber U, Werner T, Vormann J, Kisters K. Myth or reality, transdermal magnesium? Nutrients 2017;9(8):813. https://pubmed.ncbi.nlm.nih.gov/28788060/
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to magnesium. EFSA Journal 2010;8(10):1807. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2010.1807
- Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals. Food Standards Agency, 2003 (magnesium guidance level 400mg a day from supplements). https://cot.food.gov.uk/sites/default/files/vitmin2003.pdf