Last updated: October 2026
Magnesium is a popular remedy for cramps, but the evidence is weak. A Cochrane review found it’s unlikely to prevent night-time leg cramps in older adults, and a trial of magnesium at bedtime worked no better than placebo. It may help if you’re actually low in magnesium. Regular calf stretching is what the NHS recommends first.
Below: what the research shows for night cramps, exercise cramps and pregnancy, which magnesium to choose if you want to try it, how much, and when cramps need a GP.
Does magnesium help cramps? The research
| Type of cramp | What the research found |
|---|---|
| Night-time leg cramps (older adults) | Cochrane review, 2020: magnesium is unlikely to give a meaningful reduction in cramps. A 2017 trial of magnesium oxide at bedtime for four weeks found no difference from placebo; both groups improved, suggesting a placebo effect. |
| Cramps in pregnancy | Conflicting results: one trial found a benefit, others didn’t. See magnesium in pregnancy. |
| Exercise cramps | No controlled trials. Exercise cramps are more linked to muscle fatigue than to low minerals. |
| Period cramps | No high-quality evidence. See magnesium for PMS. |
That doesn’t mean magnesium does nothing for muscles: it contributes to normal muscle function and electrolyte balance. But if your magnesium intake is already adequate, extra is unlikely to stop cramps.
What causes cramps?
Often there’s no clear cause. Common triggers include:
- muscle tiredness after exercise or long periods standing
- tight calf muscles and sitting or lying awkwardly
- getting older, pregnancy, and dehydration
- some medicines, such as diuretics and statins
- conditions such as diabetes, liver or kidney disease, and nerve problems
Who might benefit from magnesium?
- People with a low intake: diets low in wholegrains, nuts, seeds and greens. See signs of magnesium deficiency.
- People on medicines that lower magnesium, such as some diuretics or long-term proton pump inhibitors (like omeprazole). Your GP can check your level with a blood test.
- Heavy drinkers and people with gut conditions that affect absorption.
Best magnesium for cramps
| Type | For cramps |
|---|---|
| Glycinate (bisglycinate) | Gentle on the stomach; good for an evening routine |
| Citrate | Well absorbed; can loosen stools |
| Oxide | Used in the night-cramp trial; cheap but less well absorbed |
| Epsom salt bath (sulphate) | Very little is absorbed through skin, but a warm bath relaxes muscles |
| Magnesium sprays and oils | Little evidence they raise magnesium levels. See magnesium spray |
Our Magnesium Glycinate Sleep Complex combines bisglycinate and citrate with glycine, L-theanine and botanicals, giving 148mg of magnesium per serving as a warm evening drink. Compare forms in types of magnesium.
How much to take
Adults need 270 to 300mg a day, mostly from food. If you supplement, 100 to 300mg a day is typical, and the NHS says 400mg or less a day from supplements is unlikely to cause harm. Give it four weeks, and if cramps haven’t changed, magnesium probably isn’t the answer for you. Speak to your GP first if you have kidney problems.
What helps cramps (NHS)
- During a cramp: stretch and massage the muscle. For a calf cramp, gently pull your toes up towards your shin.
- To prevent cramps: regular calf stretches, especially before bed.
- Afterwards: painkillers such as paracetamol or ibuprofen can ease lingering soreness.
- If these don’t help, a GP may review your medicines or, rarely, prescribe quinine.
Muscle soreness after exercise is different from cramp. See magnesium for muscle pain and CBD balm.
Cramping after heavy sweating? See electrolytes: do you need them?
When to see a GP
See a GP if cramps are frequent, affect your sleep or daily life, started after a new medicine, or come with muscle weakness, numbness or swelling. Get urgent help if one leg is swollen, red, warm and painful, as it could be a blood clot.
For what to do when cramps wake you, see leg cramps at night.
FAQs
Does magnesium help leg cramps?
Probably not for most people. A Cochrane review found it’s unlikely to prevent night-time leg cramps in older adults. It may help if you’re low in magnesium.
What is the best magnesium for cramps?
No form has been proven to stop cramps. If you want to try it, glycinate is gentle on the stomach and suits an evening routine.
How long does magnesium take to work for cramps?
Give it about four weeks. If cramps haven’t improved, magnesium is unlikely to be the answer.
What is the fastest way to stop a leg cramp?
Stretch and massage the muscle. For a calf cramp, gently pull your toes up towards your shin.
Do Epsom salt baths help cramps?
Very little magnesium is absorbed through the skin, but a warm bath can relax tight muscles.
Can low magnesium cause cramps?
Yes, a real deficiency can cause muscle cramps and twitches. A GP can check your level with a blood test.
Sources
- Garrison SR et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev, 2020.
- Roguin Maor N et al. Effect of magnesium oxide supplementation on nocturnal leg cramps. JAMA Intern Med, 2017.
- Luo L et al. Interventions for leg cramps in pregnancy. Cochrane Database Syst Rev, 2020.
- NHS. Leg cramps.
- NHS. Vitamins and minerals: magnesium.
