Magnesium for Muscle Cramps (2026): What the Evidence Actually Shows
For most cramps, magnesium probably does not help. A Cochrane review of 11 trials found it unlikely to help the night cramps of older adults. Two trials found a benefit: magnesium oxide for night leg cramps (Barna 2021), and magnesium glycinate for leg cramps in pregnancy (Supakatisant 2015).
The short answer
- Ordinary night cramps in older adults: 5 trials; Cochrane found magnesium unlikely to help (Garrison 2020).
- Night leg cramps, one newer trial: a 226 mg magnesium oxide capsule at bedtime cut cramps by 3.4 a person over 60 days, against 2.6 on a placebo (Barna 2021).
- Pregnancy leg cramps: 300 mg of magnesium bisglycinate a day for 4 weeks halved cramps in more women than a placebo did (Supakatisant 2015); other pregnancy trials did not agree. Exercise: never tested.
If you want to try it for night cramps, copy that trial: one magnesium oxide tablet at bedtime for 60 days, then stop if nothing changes. If you are pregnant, ask your prenatal provider first. Cramps that are frequent, severe or new need a doctor, because magnesium does not treat what causes them.
A summary of published trials, not medical advice. Prices are each brand’s own list price, checked October 14, 2026; Amazon’s can differ.
What the Cochrane review found
Cochrane reviews pool every good trial on a question. The 2020 update on magnesium for muscle cramps found 11 trials with 735 people, and split them by the kind of cramp (Garrison 2020).
| Cramp type | Trials | People | What they found |
|---|---|---|---|
| Ordinary cramps, mostly older adults at night | 5 | 271 | Small differences in how often, how hard or how long, none clear enough to count |
| Pregnancy leg cramps | 5 | 408 | Trials disagree; all at high risk of bias |
| Exercise cramps | 0 | 0 | Never tested |
| Cramps from a disease (liver cirrhosis) | 1 | 29 | Too small to tell |
The authors’ conclusion, word for word: It is unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps.
Side effects were mostly stomach upset such as diarrhoea, in 11% to 37% of people on magnesium against 10% to 14% on a placebo.
| Item | Value |
|---|---|
| Magnesium oxide | 3.4 fewer cramps |
| Placebo | 2.6 fewer cramps |
The positive night-cramp trial
In Ukraine, 175 adults with night leg cramps took a capsule each night for 60 days: either 226 mg of magnesium as magnesium oxide, or a placebo. Both groups had far fewer cramps by the end, which happens in most cramp trials. The magnesium group did better on top of that: 3.4 fewer cramps a person against 2.6, shorter cramps and better sleep. Nobody had a serious side effect (Barna 2021).
It is one trial, and the Cochrane review that came before it found no clear benefit in similar people. So it is worth a try if night cramps bother you, not a sure thing.
Leg cramps in pregnancy: the glycinate trial
In Thailand, 86 pregnant women who had leg cramps at least twice a week took 300 mg of magnesium bisglycinate a day, or a placebo, for 4 weeks. Cramps fell by half or more in 86% of the magnesium group against 61% of the placebo group, and the cramps that were left were milder. Side effects such as nausea and diarrhea were no more common than on the placebo (Supakatisant 2015).
Other pregnancy trials did not agree, and all were small (Garrison 2020). Pregnancy raises the RDA by 40 mg (350 to 400 mg a day, by age). Ask your prenatal provider before adding a supplement.
If you want to try magnesium
Pick the form that matches the trial for your kind of cramp. For night leg cramps, oxide is what was tested. For leg cramps in pregnancy, glycinate is what was tested (ask your prenatal provider first). For ordinary night cramps in older adults, the Cochrane review found magnesium unlikely to help, whatever the form.
| Product | Serving | Per 300 mg | Buy |
|---|---|---|---|
| Nature Made Magnesium Oxide (for night cramps: the night-cramp trial’s form) | 250 mg in 1 tablet | $0.071 | Check price |
| Nature Made Magnesium Glycinate (for pregnancy cramps: the pregnancy trial’s form; USP Verified) | 200 mg in 2 capsules | $1.10 | Check price |
| KAL Magnesium Glycinate 350 (also glycinate) | 240 capsules, about 88 mg each. One serving (4 capsules, 350 mg) is the whole limit. Not on a testing list. | No list price we could check | Check price |
| BulkSupplements Magnesium Glycinate Powder (a glycinate and oxide blend; matches neither trial exactly) | 300 mg in ¾ teaspoon (2.2 g) | $0.19 | Check price |
- If you have kidney disease, ask your doctor before you take magnesium. Weak kidneys cannot clear the extra, so it can build up (NIH).
- Water pills: loop and thiazide diuretics make you lose more magnesium; potassium-sparing ones make you lose less (NIH). Heartburn pills (PPIs such as esomeprazole or lansoprazole), taken for a year or more, can lower magnesium.
What else helps cramps
No magnesium trial covers cramps during or after exercise (Cochrane found none). If cramps come with weakness, swelling or a new medicine, see a doctor. If you think you run low on magnesium, see signs of magnesium deficiency.
Frequently asked questions
Does magnesium help with muscle cramps?
For most people, probably not. A Cochrane review of 11 trials found no clear drop in how often, how hard or how long cramps hit older adults who took magnesium. One later trial of 175 adults with night leg cramps did find a small benefit: about 3.4 fewer cramps over 60 days on magnesium, against 2.6 fewer on a placebo (Barna 2021).
What type of magnesium is best for muscle cramps?
No form is proven best. It depends on the cramps. For night leg cramps, the one positive trial used magnesium oxide, a 226 mg capsule at bedtime (Barna 2021), so oxide is the match. For leg cramps in pregnancy, the positive trial used magnesium bisglycinate, 300 mg a day (Supakatisant 2015), so glycinate is the match; ask your prenatal provider first.
Does magnesium help leg cramps at night?
One trial says a little. In Barna 2021, adults with night leg cramps who took magnesium oxide at bedtime for 60 days had fewer cramps than those on a placebo, and both groups improved a lot. The Cochrane review, which pooled 5 trials in older adults with ordinary night cramps, found no clear benefit.
Does magnesium help cramps in pregnancy?
Maybe. In one trial of 86 pregnant women, 300 mg of magnesium bisglycinate a day for 4 weeks cut cramps by half or more in 86% of women, against 61% on a placebo, and the cramps were milder (Supakatisant 2015). Cochrane found 5 pregnancy trials in 408 women in all; they did not agree, and all were at high risk of bias. Ask your prenatal provider before you take any supplement.
Does magnesium help cramps from exercise?
Nobody has tested it. Cochrane found no randomized trials of magnesium for cramps during or after exercise.
How much magnesium is safe to take for cramps?
The upper limit for adults is 350 mg a day of magnesium from supplements and medicines. Food does not count toward it (NIH). The trial that helped night cramps used one 226 mg magnesium oxide capsule a day; the pregnancy trial used 300 mg of magnesium bisglycinate a day.
Related
- Magnesium deficiency symptoms · how much magnesium per day · side effects
- Best magnesium supplements · best magnesium for sleep · all forms compared
- Electrolytes guide · magnesium guide
Sources
- Garrison SR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020. PubMed 32956536
- Barna O, et al. A randomized, double-blind, placebo-controlled, multicenter study assessing the efficacy of magnesium oxide monohydrate in the treatment of nocturnal leg cramps. Nutr J. 2021. PubMed 34719399
- Supakatisant C, Phupong V. Oral magnesium for relief in pregnancy-induced leg cramps: a randomised controlled trial. Matern Child Nutr. 2015. PubMed 22909270
- NIH Office of Dietary Supplements. Magnesium fact sheet for health professionals (updated January 6, 2026).
- Labels and prices: Nature Made and BulkSupplements pages, list prices checked October 14, 2026; KAL’s serving from its Amazon listing.