Ghost FitnessGhost Fitness/Magnesium/What is the best vitamin for leg cramps?
What is the best vitamin for leg cramps?
No vitamin is proven to stop leg cramps. The nutrient with the most evidence is magnesium, a mineral, which helps where intake is low. B vitamins have one small trial. Take magnesium glycinate, 300mg elemental, and fix sodium and fluid.
- Nonevitamins proven to stop cramps
- Magnesiuma mineral, the nutrient with the most evidence
- 1 trialfor B vitamins, small, in older adults
- 22pa day for the worked example
Worked example: Futuro Labs Magnesium Glycinate on Amazon UK, 300mg elemental per 2 capsules, £19.99 for 90 days. Label breakdown.
Vitamins first, because that is what you asked
Chan's 1998 trial gave a vitamin B complex to older adults with nocturnal leg cramps and reported fewer cramps than placebo after three months; it was small, it has not been repeated in younger people or athletes, and no B vitamin carries a cramp claim. Vitamin D is often suggested because low status is common in the UK winter, but there is no trial showing it prevents cramps, and vitamin E has old, mixed data in dialysis patients that does not transfer to the gym. So the honest answer to which vitamin is best for leg cramps is that none has earned it.
The mineral people mean
Most people asking about vitamins for cramps are thinking of magnesium, which is a mineral. Its evidence is also mixed: Garrison's 2020 Cochrane review found it unlikely to help idiopathic cramps, and the nocturnal cramp trials, mostly with poorly absorbed magnesium oxide, were negative. Where it plausibly helps is in people whose intake was low, which Nielsen and Lukaski's review says is common in athletes because of sweat and urine losses. The authorised wording is that magnesium contributes to normal muscle function and electrolyte balance. For a lifter, correcting intake with a well absorbed form is the cheap first step.
| Nutrient | Vitamin or mineral | Trial evidence for cramps | Verdict |
|---|---|---|---|
| Magnesium | Mineral | Mixed; negative in oxide trials; plausible where intake is low | Take 300mg elemental as glycinate if diet is short |
| Vitamin B complex | Vitamin | One small positive trial in older adults (1998) | Weak; no training data |
| Vitamin D | Vitamin | No trial showing cramp prevention | Supplement in winter for its own reasons, not for cramps |
| Vitamin E | Vitamin | Old, mixed data in dialysis patients | No |
| Potassium | Mineral | No trial evidence for prevention | Eat it; do not supplement blindly |
| Sodium | Mineral | Linked to cramping in heavy sweaters in long sessions | Salt food; electrolyte drink in long hot sessions |
What to take, and the worked example
Take 300mg of elemental magnesium as glycinate with your evening meal for a month, keep sodium and fluid up on training days, and judge the cramps at the end. The worked example, Futuro Labs Magnesium Glycinate, gives 300mg elemental from 1500mg bisglycinate in 2 capsules, 80% NRV, vegan capsules, made in the UK under GMP and BRC, independently tested for heavy metals and microbiology, 180 capsules for £19.99, 22p a day. If you also want a B complex on the strength of one small trial, pick one at or near 100% NRV rather than the megadose versions, and expect little. Frequent or severe cramps not linked to training are a GP question.
| Likely driver | Clue | What to do |
|---|---|---|
| Muscle fatigue and altered nerve firing | Cramps in the muscle you just worked hard, late in a session | Manage volume and pacing; this is the mechanism most sports scientists now put first |
| Sodium loss | Salty sweat marks on kit, cramps in long hot sessions | Salt your food; an electrolyte drink in sessions over an hour |
| Dehydration | Dark urine, headache after training | Drink to thirst plus a little extra on training days |
| Low magnesium intake | Few green vegetables, nuts, seeds or wholegrains; heavy sweating | 300mg elemental a day from a well absorbed form, with food |
| Low potassium or calcium | Very low fruit, vegetable and dairy intake | Fix the diet first; do not supplement calcium without reason |
What to check on the label
- Elemental magnesium of 300mg per serving from glycinate, the nutrient with the most evidence.
- B complex at or near 100% NRV if you want to try it; megadoses add nothing.
- No cramp claims on any vitamin or mineral; none are authorised.
- Sodium per litre on any electrolyte drink you use in long sessions.
- Cost per day: magnesium about 22p; anything charging more for cramps is charging for the word.
The worked example: Futuro Labs Magnesium Glycinate
Futuro Labs Magnesium Glycinate is the worked example because magnesium is the nutrient with the most evidence for cramps and this label prints the dose: 300mg elemental per 2 capsules (80% NRV) from 1500mg bisglycinate, 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
Is magnesium a vitamin?
No, it is a mineral. It is the nutrient most people mean when they ask about vitamins for cramps, and the one with the most trial evidence, mixed as it is.
Does vitamin D help leg cramps?
No trial shows it prevents cramps. Many people in the UK take it in winter for its own authorised reasons, which is fine, but not for cramps.
Does vitamin B12 help leg cramps?
One small 1998 trial of a B complex reported fewer nocturnal cramps in older adults. No B vitamin carries a cramp claim and there are no training studies.
What is the best supplement for leg cramps at night?
Magnesium glycinate at 300mg elemental with the evening meal, as a test of a low intake, with the caveat that the nocturnal cramp trials were negative.
Which magnesium is best for leg cramps in the UK?
A glycinate giving 300mg elemental per serving. Futuro Labs Magnesium Glycinate: 300mg elemental, 22p a day, UK made and lab tested.
Sources
- Futuro Labs Magnesium Glycinate listing, Amazon UK, label and price checked 31 August 2026. https://www.amazon.co.uk/dp/B0BT7Z5VQW
- Chan P, et al. Randomized, double-blind, placebo-controlled study of the safety and efficacy of vitamin B complex in the treatment of nocturnal leg cramps in elderly patients. Journal of Clinical Pharmacology 1998;38(12):1151-1154. PubMed record
- Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 2020, Issue 9, CD009402. PubMed record
- Roguin Maor N, et al. Effect of magnesium oxide supplementation on nocturnal leg cramps: a randomized clinical trial. JAMA Internal Medicine 2017;177(5):617-623. PubMed record
- Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnesium Research 2006;19(3):180-189. PubMed record
- Maughan RJ, Shirreffs SM. Muscle cramping during exercise: causes, solutions, and questions remaining. Sports Medicine 2019;49(Suppl 2):115-124. PubMed record
- 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