Can you take too much magnesium for leg cramps?

The escalation ladder, rung by rung, because too much magnesium for cramps happens in a sequence

Can you take too much magnesium for leg cramps is answered by the sequence in which it happens, because nobody sets out to take too much and almost everybody who does climbed a ladder one rung at a time. Rung one, 200 to 300mg elemental: a reader with night cramps or exercise cramps reads that magnesium helps, starts a labelled dose, and finds after a few weeks that the cramps continue, because the trials find magnesium unlikely to help ordinary skeletal muscle cramps, the Cochrane review and the oxide trial, and exercise cramps are neuromuscular fatigue, so the dose did nothing for the cramps while doing its honest job for a reader who happened to be short, whose cramps, if they were a shortfall's, would ease over days to weeks. Rung two, 400 to 500mg: the reader concludes the dose was too low, climbs to or over the UK guidance level of about 400mg supplemental, and meets the osmotic laxative effect, loose stools within hours of a dose that exceeds absorption, citrate and oxide first and bisglycinate last, with the cramps unchanged because a larger dose of something that does not treat cramps still does not. Rung three, 800mg and up: the reader climbs again, often by adding a second product or a magnesium laxative, and produces frank diarrhoea, which loses potassium, sodium and fluid, and low potassium and dehydration are established cramp causes, so the cramps get worse, the cramps-from-excess page's indirect route, and the reader is now taking too much magnesium for leg cramps in the fullest sense, a laxative dose that has manufactured a new reason to cramp, with hypermagnesaemia still out of reach in working kidneys but the gut and the electrolytes in disarray.

The exit, which is not another rung, and the ladder filed

The exit from the ladder is not a fourth rung, and the reader on rung three takes three steps down and one sideways. Down: the dose returns to a labelled 300mg elemental as bisglycinate, or stops, the diarrhoea settling within a day, fluids and a salty meal restoring what it took, potassium-rich food, bananas, potatoes, beans and yoghurt, replacing the potassium, and the cramps the ladder caused easing as the electrolytes return. Sideways: the cramp toolkit that has evidence, stretching the calves before bed and during a cramp, loosening the bedding or a pillow under the knees, light movement on sedentary days, hydration with sodium after long hot sessions, and a pharmacist's review of cramping medicines, diuretics, statins and asthma inhalers among them, the night-cramp cause list's steps. And the panel, for cramps that continue: a GP's routine electrolyte panel, sodium, potassium and calcium with magnesium added, kidney function and glucose, vitamin D and thyroid where warranted, which settles in one blood test whether any deficiency was ever involved and which, if it finds a low magnesium, is answered by a labelled dose with the cause closed rather than by rung three. A GP also for cramps that are frequent, severe, one-sided or accompanied by swelling, weakness or numbness. The ladder filed: rung one does nothing for cramps and everything for a shortfall, rung two loosens the stools, rung three manufactures cramps from lost electrolytes, and the exit is down to a labelled dose and sideways to the toolkit and a panel, the worked example being a labelled dose that stays on rung one, bisglycinate at 300mg elemental, £19.99 for 90 days at 22p, taken for a shortfall by audit and never escalated for a cramp.

The verdict, a ladder to climb down rather than up

Can you take too much magnesium for leg cramps: yes, by climbing an escalation ladder, a labelled dose doing nothing for ordinary cramps because magnesium does not treat them, a doubled dose loosening the stools, and a tripled dose or an added laxative producing diarrhoea that loses potassium and fluid and makes the cramps worse, with the exit being down to a labelled dose with fluids, salt and potassium-rich food, sideways to the cramp toolkit of stretching, bedding, movement, hydration and a medicine review, and to a GP's electrolyte panel for cramps that continue. The labelled dose that stays on rung one: Futuro Labs Magnesium Glycinate, bisglycinate, 300mg elemental at 80% NRV, £19.99 for 90 days at 22p a day, for a shortfall by audit and never escalated for a cramp.

What to check on the label

Questions people also ask

How much magnesium is too much for leg cramps?

Anything above a labelled dose taken in the hope of more relief: 400 to 500mg elemental loosens the stools and 800mg or a magnesium laxative produces diarrhoea that loses potassium and fluid and makes cramps worse, since magnesium does not treat ordinary cramps at any dose.

Why did my cramps get worse when I increased my magnesium?

The diarrhoea of a surplus dose lost potassium, sodium and fluid, and low potassium and dehydration are established cramp causes, so the higher dose manufactured a new reason to cramp, fixed by climbing down to a labelled dose with fluids, salt and potassium-rich food.

Does a higher dose of magnesium work better for cramps?

No: the trials find magnesium unlikely to help ordinary skeletal muscle cramps, and exercise cramps are neuromuscular fatigue, so a larger dose of something that does not treat cramps adds side effects without relief; only a genuine shortfall's cramps respond, at a labelled dose over weeks.

What should I do instead of taking more magnesium for cramps?

The toolkit with evidence: stretch the calves before bed and during a cramp, loosen the bedding or put a pillow under the knees, move lightly on sedentary days, hydrate with sodium after long hot sessions, and review cramping medicines with a pharmacist.

Should I get a blood test for my cramps?

For cramps that continue after the toolkit, yes: a GP's electrolyte panel with magnesium added settles in one test whether any deficiency was involved, and a low result is answered by a labelled dose with the cause closed rather than by escalation.

Sources

1. Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 2020, Issue 9, CD009402. PubMed record
2. The hypermagnesaemia literature: raised serum magnesium is rare with normal kidney function and occurs with impaired excretion or massive intake from magnesium laxatives and antacids, presenting with nausea, lethargy, low blood pressure, muscle weakness and slowed heart conduction, and treated in hospital with intravenous calcium and, where needed, dialysis. PubMed record
3. 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
4. The hypomagnesaemia literature: clinically low serum magnesium presents with cramps, tremor, weakness and, when severe, arrhythmias and seizures, with alcohol misuse, proton-pump inhibitors, diuretics and gastrointestinal loss the common causes, and serum magnesium an imperfect marker of tissue status. PubMed record

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