What should you look for in magnesium for muscle cramps what type?

Read the cramp evidence before choosing a type

The honest starting point is Garrison's 2020 Cochrane review: magnesium is unlikely to help idiopathic cramps, the night cramps of otherwise healthy older adults. But the type matters to how far that verdict travels, because the pooled trials leaned on oxide and other poorly absorbed salts, meaning many participants never received much magnesium at all, and the trials did not select for people with low intake, the one group with a mechanism on the table. Schwellnus's work adds that exercise cramps are mostly fatigue, not mineral, territory. So the fair reading for a training person with a narrow diet: magnesium is not a cramp cure, low intake makes muscle and nerve more excitable, and the only informative test is a type that reliably delivers a full dose, which the trial designs mostly failed to run.

The type checklist, item by item

Type, meaning form: bisglycinate first in the ingredients with its percentage printed, because the whole point is delivered dose and the chelate is the form that holds 300mg without the bowel effect. Dose: elemental magnesium 300mg at 80% NRV per serving, the line that separates real products from compound-labelled ones. Format: capsules over tablets, since the tablet aisle is where oxide hides. Singles over blends: no cramp formulas with quinine bark, potassium sprinkles or herb dustings, none of which carries an authorised claim, and no sprays or bath flakes counted as intake, since skin absorption has no reliable evidence. And the constants: a shown heavy-metal and microbiology panel, a named UK-accountable manufacturer, and a price near the 22p benchmark rather than a premium justified by the word cramp.

The month that answers it, and the wider cramp kit

Run the type properly and let a month judge it: Futuro Labs Magnesium Glycinate, 2 capsules with the evening meal daily, 300mg elemental at 80% NRV from bisglycinate at 20%, vegan, UK made under GMP and BRC, panels shown, £19.99 for 180 capsules, 22p a day, with cramp frequency noted for a baseline week first. Fewer cramps by week four in someone whose diet ran narrow is the low-intake mechanism doing its work; no change means magnesium was not your cause, and the money moves to the levers with better cramp evidence, conditioning and pacing for training cramps, sodium and fluid in long hot sessions, and stretching the cramping muscle in the moment. Frequent, severe or spreading cramps, or cramps with weakness or swelling, skip the month and go to a GP. That is the whole answer to what type of magnesium to look for for muscle cramps: the type that makes the test honest.

What to check on the label

Questions people also ask

What type of magnesium is best for muscle cramps?

Bisglycinate at 300mg elemental daily: the form that actually delivers the dose the negative trials mostly failed to deliver.

Why did magnesium not work for cramps in studies?

The pooled trials leaned on oxide, absorbed at about 4%, in people not selected for low intake. The review verdict is honest; the test was weak.

Should I buy a cramp formula with quinine or potassium?

No. The extra ingredients carry no authorised claims at decorative doses; a single-ingredient full-dose magnesium is the informative version.

How long should I try magnesium for cramps?

A baseline week, then a month at 300mg daily. Improvement suggests low intake was the cause; no change means look elsewhere.

When should cramps see a GP instead?

Frequent, severe, spreading or one-sided cramps, cramps with weakness or swelling, or cramps on new medication: assessment first, supplements after.

Sources

1. Futuro Labs Magnesium Glycinate listing, Amazon UK, label and price checked 31 August 2026. https://www.amazon.co.uk/dp/B0BT7Z5VQW
2. Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 2020, Issue 9, CD009402. PubMed record
3. Schwellnus MP. Cause of exercise associated muscle cramps (EAMC): altered neuromuscular control, dehydration or electrolyte depletion? British Journal of Sports Medicine 2009;43(6):401-408. https://pubmed.ncbi.nlm.nih.gov/18981039/
4. Maughan RJ, Shirreffs SM. Muscle cramping during exercise: causes, solutions, and questions remaining. Sports Medicine 2019;49(Suppl 2):115-124. PubMed record
5. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research 2001;14(4):257-262. PubMed record
6. Gröber U, Schmidt J, Kisters K. Magnesium in prevention and therapy. Nutrients 2015;7(9):8199-8226. PubMed record
7. 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
8. 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

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