What causes low magnesium?

The causes ranked by how common they are, and the line between mild and clinical

What causes low magnesium is a list best ranked by how common each cause is, because the commonest cause is mild and the rarest are serious, and a reader usually belongs near the top. First and commonest, a diet that runs short: magnesium is a volume nutrient spread through leafy greens, nuts, seeds, legumes, wholegrains and dark chocolate, and a diet built on refined carbohydrate, meat and processed food supplies less than the reference intake for a large share of the population, producing marginal status, tiredness, cramps and a duller stress response by association, rather than clinical deficiency, the cause a diet audit catches and a supplement or a change of plate corrects, and the cause every lifter on a cut or a rice-and-chicken bulk should suspect first. Second, alcohol: heavy and sustained drinking raises urinary magnesium loss and reduces intake, and is the commonest cause of clinically low magnesium in otherwise-fed adults, the drain no supplement outruns while the drinking continues. Third, medicines: proton-pump inhibitors over long use reduce gut absorption, loop and thiazide diuretics raise urinary loss, and some antibiotics, chemotherapy agents and other drugs lower magnesium, all of which are a pharmacist's conversation and often the reason a doctor recommends magnesium. Fourth, gut loss: chronic diarrhoea, inflammatory bowel disease, coeliac disease, short bowel and weight-loss surgery all reduce absorption or increase loss, the cause a gastroenterologist manages. Fifth, poorly controlled diabetes: high blood sugar raises urinary magnesium loss through osmotic diuresis, low magnesium being common in diabetes and improving with glucose control. Sixth, ageing: intestinal absorption falls and urinary loss rises with age, and older adults on several medicines accumulate causes. Seventh and rarest, genetic conditions of the kidney tubule that waste magnesium, a specialist's diagnosis.

What the ranking means for a reader, how low magnesium is found, and the causes filed

The ranking means something practical: a healthy lifter with tiredness and a diet light in magnesium foods has the first cause and corrects it with food or a supplement, and a reader with a cause further down the list has a reason to see a doctor, because the supplement treats the symptom of a drain it cannot stop, the alcohol, the medicine, the gut disease or the glucose being the thing to address. How low magnesium is found is worth stating because the blood test disappoints: serum magnesium is held in a narrow range at the expense of bone and muscle, so a normal serum result does not exclude marginal tissue status and a low serum result is a real finding that usually has a cause from the lower list, which is why this site puts the diet audit before the blood test for the mild version and the GP with a blood test for anyone with a cause or symptoms that warrant it, the low-magnesium danger page's grading of severe deficiency as rare, caused and treated. The causes filed: a short diet first and commonest, correctable by food or a supplement within guidance; alcohol, medicines, gut loss, diabetes, ageing and genetics next, each a cause to address with a professional while a supplement holds status; and the worked example being the answer to the first cause and a support for the others on advice, bisglycinate at 300mg elemental and 80% NRV with the evening meal, £19.99 for 90 days at 22p.

The verdict, usually the plate and sometimes a doctor

What causes low magnesium: ranked by how common, a diet short of greens, nuts, seeds, legumes and wholegrains first and mildest, then alcohol as the commonest clinical cause, then medicines, proton-pump inhibitors and diuretics, then gut loss from diarrhoea, bowel disease, coeliac disease or weight-loss surgery, then poorly controlled diabetes, then ageing, then rare genetic conditions, with the mild dietary version corrected by food or a supplement and every other cause addressed with a professional while a supplement holds status. For the first cause: Futuro Labs Magnesium Glycinate, bisglycinate, 300mg elemental at 80% NRV, £19.99 for 90 days at 22p a day.

What to check on the label

Questions people also ask

What is the most common cause of low magnesium?

A diet light in the foods that carry it, leafy greens, nuts, seeds, legumes and wholegrains, which produces marginal status rather than clinical deficiency and is corrected by food or a supplement within guidance.

Does alcohol cause low magnesium?

Yes, and it is the commonest cause of clinically low magnesium in otherwise-fed adults: heavy sustained drinking raises urinary loss and lowers intake, a drain no supplement outruns while the drinking continues.

Which medicines lower magnesium?

Proton-pump inhibitors over long use, which reduce gut absorption, loop and thiazide diuretics, which raise urinary loss, and some antibiotics and chemotherapy agents, all a pharmacist's conversation and often a reason a doctor recommends magnesium.

Can gut problems cause magnesium deficiency?

Yes: chronic diarrhoea, inflammatory bowel disease, coeliac disease, short bowel and weight-loss surgery reduce absorption or increase loss, the causes a gastroenterologist manages.

Why might my blood test be normal when I feel low in magnesium?

Serum magnesium is held in a narrow range at the expense of bone and muscle, so a normal result does not exclude marginal tissue status; a diet audit comes first, and a GP test follows where symptoms or a cause warrant it.

Sources

1. 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
2. The magnesium and medicines literature: magnesium supplements reduce absorption of tetracycline and quinolone antibiotics, bisphosphonates and levothyroxine when taken together and are spaced from them, while proton-pump inhibitors and some diuretics lower magnesium status, a reason for medical advice in either direction. PubMed record
3. Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects 41, 1991 (magnesium RNI 300mg men, 270mg women).
4. 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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