Magnesium and muscle cramps: does topping up really help?

Topping up magnesium helps against muscle cramps less than the ads suggest. A large review found little evidence that magnesium supplements reduce cramps in most adults (Garrison, 2020). Still, a real deficiency can go with cramp. The difference lies in the cause of your cramp.

I get the appeal: one pill and done. Only your body rarely works that simply, and you deserve to know that before you buy a tub.

Does magnesium really help against muscle cramps?

For most people with ordinary cramps, the effect of extra magnesium is small to absent. That's because most cramps don't arise from a magnesium deficiency. If you do have a proven deficiency, topping up can make sense, but that's a different situation from just taking it preventively.

Saying it flatly would be too easy, so let me keep it nuanced: magnesium isn't a miracle cure, but with a deficiency it's relevant.

What does the research say?

A Cochrane review pooled several studies on magnesium and muscle cramps. The conclusion: for general, often nocturnal cramps in adults, magnesium is unlikely to make a clinically meaningful difference (Garrison, 2020). In pregnant women and specific groups the picture was less clear.

That's useful information if you're unsure whether to start the supplements. The money often goes on something with little demonstrable effect.

There's more on sport, muscles and recovery in the pillar blood values for athletes.

When can a magnesium deficiency play a role?

A real deficiency is less common, but can occur with certain bowel problems, heavy alcohol use, some medicines or a long one-sided diet. Besides cramp, a deficiency can go with fatigue and tingling. A low magnesium in your blood can make such a deficiency visible.

Note: your blood value doesn't always tell the whole story, because most magnesium sits in your cells and bones. So discuss a low value with your GP.

What other causes of cramp are there?

Cramp often has several causes at once. The table below lists a few common situations and whether magnesium is likely to do anything about them.

Food first: where is magnesium found?

Before you think of pills: magnesium is in many ordinary foods. Wholegrain cereals, nuts, legumes, green vegetables and seeds are good sources (Voedingscentrum). A varied diet usually supplies enough.

If you train a lot and sweat heavily, also watch your total fluid and salt intake. Often there's more to gain there than in a single supplement.

When a blood test or GP?

If cramps keep coming back, are severe, or come with other symptoms such as muscle weakness, discuss it with your GP. A blood test can show a deficiency, but the GP looks more broadly at possible causes. See also muscle complaints after exercise.

See your result as a starting point for that conversation, not a diagnosis.

So what does help against cramp?

If magnesium usually does little, what does? For sport cramp, building up calmly, hydrating well and watching your salt intake often make more sense than a pill. Stretching and relaxing the muscle helps in the moment, though the evidence for that is limited too.

For nocturnal calf cramps, some people choose stretching exercises before sleep. The evidence isn't strong, but the risk is small and it costs you nothing. Patience matters here: cramps often come and go on their own.

If the cramps stay severe or stubborn, don't keep stacking supplements endlessly. Discuss it with your GP, who can look at underlying causes that a tub of magnesium would miss.

Getting started

If you want to measure your magnesium among other things, the Vegetarian panel maps a number of nutrition-related markers, including magnesium. Handy if you eat little or no animal products.

References

1. Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;9:CD009402. PMID 32956536.
2. Voedingscentrum. Magnesium: sources and function.
3. Thuisarts.nl. I have muscle cramp. Dutch College of General Practitioners.

Disclaimer

Caliberhealth works with BIG-registered doctors who assess your blood results. This article gives general information and is not a substitute for medical advice from a GP or specialist. A blood test is a tool, not a diagnosis in itself. For serious symptoms, contact your GP, or in an emergency call 112.