https://magnesiumguide.uk/ An independent UK guide to magnesium: how much you need, which form to take, what trials show for sleep, cramps and migraine, and how to take it safely. en-gb https://magnesiumguide.uk/benefits/blood-sugar-and-diabetes/ https://magnesiumguide.uk/benefits/blood-sugar-and-diabetes/ Thu, 05 Nov 2026 00:00:00 GMT A little, mainly in people who are short of magnesium. Trials in type 2 diabetes found slightly lower fasting blood sugar, about 0.5 mmol/L on average, but no clear change in HbA1c. In prediabetes, magnesium lowered blood sugar after a glucose drink. It is an add-on to diet, activity and medicines, not a replacement. https://magnesiumguide.uk/benefits/sleep/ https://magnesiumguide.uk/benefits/sleep/ Wed, 04 Nov 2026 00:00:00 GMT Possibly a little. Small placebo-controlled trials found magnesium helped people fall asleep about 17 minutes faster on average, or modestly improved insomnia scores. The best-quality recent trial, using magnesium bisglycinate, found a small benefit. People with low magnesium intakes seem to gain most. https://magnesiumguide.uk/benefits/blood-pressure/ https://magnesiumguide.uk/benefits/blood-pressure/ Wed, 04 Nov 2026 00:00:00 GMT Yes, slightly. A meta-analysis of 34 double-blind trials found about 368 mg of magnesium a day for three months lowered blood pressure by around 2 mmHg. The fall was about twice as large in people with insulin resistance, prediabetes or other long-term conditions. It is not a substitute for blood pressure medicine. https://magnesiumguide.uk/forms/epsom-salts-and-sprays/ https://magnesiumguide.uk/forms/epsom-salts-and-sprays/ Wed, 04 Nov 2026 00:00:00 GMT There is no good evidence that magnesium baths, flakes, oils or sprays raise the body's magnesium. Skin is an effective barrier to charged minerals, and a 2017 review concluded that transdermal magnesium is scientifically unsupported. A warm bath may still help you relax, but if you need magnesium, take it by mouth or eat more magnesium-rich food. https://magnesiumguide.uk/basics/food-sources/ https://magnesiumguide.uk/basics/food-sources/ Wed, 04 Nov 2026 00:00:00 GMT The richest everyday sources of magnesium are seeds (especially pumpkin and chia), nuts (almonds, cashews, peanuts), beans and lentils, wholegrains, and cooked dark leafy greens such as spinach. A 28 g handful of pumpkin seeds has about 156 mg, roughly half a woman's daily reference intake. https://magnesiumguide.uk/basics/how-much-magnesium-do-you-need/ https://magnesiumguide.uk/basics/how-much-magnesium-do-you-need/ Wed, 04 Nov 2026 00:00:00 GMT Adults in the UK need about 300 mg of magnesium a day for men and 270 mg for women aged 19 to 64, mostly from food. The NHS says 400 mg a day or less from supplements is unlikely to cause harm. Food magnesium doesn't count towards that limit, because the kidneys clear any excess from food easily. https://magnesiumguide.uk/buying-guide/ https://magnesiumguide.uk/buying-guide/ Wed, 04 Nov 2026 00:00:00 GMT Check three things: the elemental magnesium per serving (not the compound weight on the front), how many capsules a serving is, and the form. Then compare the cost per 100 mg of magnesium, which our calculator works out. For most people, a plain citrate or glycinate product is good value; expensive blends rarely add anything proven. https://magnesiumguide.uk/how-to-take/ https://magnesiumguide.uk/how-to-take/ Wed, 04 Nov 2026 00:00:00 GMT Most adults who need a supplement take 100 to 300 mg of elemental magnesium a day, with food, in one or two doses. Stay at or below 400 mg a day from supplements unless a doctor advises more. Keep it two to four hours apart from medicines it can block, and give it about a month before judging whether it helps. https://magnesiumguide.uk/safety/ https://magnesiumguide.uk/safety/ Wed, 04 Nov 2026 00:00:00 GMT For most healthy adults, magnesium supplements are safe at up to 400 mg a day, the level the NHS says is unlikely to cause harm. The commonest side effect is diarrhoea. People with kidney disease should avoid supplements unless their doctor advises them, and magnesium can block the absorption of some antibiotics, osteoporosis tablets and levothyroxine. https://magnesiumguide.uk/safety/drug-interactions/ https://magnesiumguide.uk/safety/drug-interactions/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium can stop some medicines being absorbed if taken at the same time, including tetracycline and quinolone antibiotics, bisphosphonates for osteoporosis and levothyroxine, so leave a gap of a few hours. Some medicines lower magnesium, especially long-term proton pump inhibitors and loop or thiazide diuretics. Ask your pharmacist if you take regular medicines. https://magnesiumguide.uk/benefits/ https://magnesiumguide.uk/benefits/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium works well as a laxative and has reasonable evidence for preventing migraine, slightly lowering blood pressure and modestly helping sleep. Evidence for anxiety, low mood and premenstrual symptoms is weak. For night-time leg cramps in older adults and menopausal hot flushes, good trials found no benefit. https://magnesiumguide.uk/basics/magnesium-blood-test/ https://magnesiumguide.uk/basics/magnesium-blood-test/ Wed, 04 Nov 2026 00:00:00 GMT The standard test measures magnesium in blood serum. Most UK labs treat roughly 0.7 to 1.0 mmol/L as normal, with small differences between labs. Because less than 1% of the body's magnesium is in the blood, a normal result does not rule out low stores, but a low result is meaningful and needs a doctor's attention. https://magnesiumguide.uk/forms/magnesium-citrate/ https://magnesiumguide.uk/forms/magnesium-citrate/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium citrate is magnesium bound to citric acid. It is about 16% magnesium by weight, dissolves easily and was absorbed better than oxide in a University of Reading trial. It is a good, affordable all-round form. At higher doses it loosens stools, which can be useful for constipation but a nuisance otherwise. https://magnesiumguide.uk/how-to-take/dosage-and-timing/ https://magnesiumguide.uk/how-to-take/dosage-and-timing/ Wed, 04 Nov 2026 00:00:00 GMT For most adults, 100 to 300 mg of elemental magnesium a day is a sensible supplement dose, and the NHS says up to 400 mg a day is unlikely to cause harm. Trials for sleep used 250 to 500 mg, for blood pressure 300 to 450 mg and for migraine about 600 mg. Doses above 400 mg are best agreed with a GP or pharmacist. https://magnesiumguide.uk/benefits/anxiety-and-stress/ https://magnesiumguide.uk/benefits/anxiety-and-stress/ Wed, 04 Nov 2026 00:00:00 GMT The evidence is weak. A systematic review found hints that magnesium may ease mild anxiety and premenstrual anxiety, but rated the studies as poor quality. A trial for depression found a large benefit but had no placebo group. Magnesium is not a treatment for an anxiety disorder or depression. https://magnesiumguide.uk/benefits/constipation/ https://magnesiumguide.uk/benefits/constipation/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium works well for constipation. Magnesium salts draw water into the bowel and soften stools, and they have been used as laxatives for well over a century. In a placebo-controlled trial, 1.5 g of magnesium oxide a day improved symptoms in 68% of people, against 12% on placebo. People with kidney disease should not use it. https://magnesiumguide.uk/benefits/muscle-cramps/ https://magnesiumguide.uk/benefits/muscle-cramps/ Wed, 04 Nov 2026 00:00:00 GMT Probably not, for most people. A Cochrane review of 11 trials found magnesium is unlikely to reduce ordinary night-time leg cramps in older adults, and the largest trial found it no better than placebo. Evidence for cramps in pregnancy is conflicting. It may help if a blood test shows your magnesium is low. https://magnesiumguide.uk/benefits/migraine/ https://magnesiumguide.uk/benefits/migraine/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium may cut how often migraines happen. In the best-known trial, 600 mg of magnesium a day reduced attacks by 42% after 12 weeks, against 16% on placebo, though another trial found no benefit. US neurology guidelines rate it as probably effective. It is a reasonable option to discuss with your GP, especially if prescribed preventers don't suit you. https://magnesiumguide.uk/benefits/restless-legs/ https://magnesiumguide.uk/benefits/restless-legs/ Wed, 04 Nov 2026 00:00:00 GMT Maybe, but the evidence is thin. One trial of 75 people in Iran found 250 mg of magnesium oxide a day eased restless legs more than placebo after two months, and two small studies without a placebo also reported improvement. A 2019 systematic review could not say whether magnesium works. Low iron is a far better-established cause to check first. https://magnesiumguide.uk/forms/magnesium-glycinate/ https://magnesiumguide.uk/forms/magnesium-glycinate/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium glycinate is magnesium bound to the amino acid glycine. It is gentle on the gut and appears well absorbed, which makes it a good choice for people who get loose stools from other forms. A 2025 placebo-controlled trial found it modestly improved insomnia scores. Claims that it is uniquely calming are not proven. https://magnesiumguide.uk/forms/magnesium-l-threonate/ https://magnesiumguide.uk/forms/magnesium-l-threonate/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium L-threonate raised brain magnesium and improved memory in rats. In people, two placebo-controlled trials reported better memory scores and better sleep, but both were linked to the company that sells the branded ingredient and neither has been repeated independently. It contains only about 8% magnesium and is the most expensive form. https://magnesiumguide.uk/forms/magnesium-oxide/ https://magnesiumguide.uk/forms/magnesium-oxide/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium oxide is 60% magnesium, so tablets are small and cheap, but only a small fraction is absorbed: about 4% in one study. Much of the rest stays in the gut and draws in water, which makes it an effective laxative. It is a poor choice for raising magnesium levels and a good one for constipation. https://magnesiumguide.uk/safety/side-effects/ https://magnesiumguide.uk/safety/side-effects/ Wed, 04 Nov 2026 00:00:00 GMT The commonest side effects of magnesium supplements are diarrhoea, loose stools, stomach cramps and nausea, especially with magnesium oxide, citrate or sulphate and at doses over 400 mg. Taking it with food, splitting the dose or switching to glycinate usually helps. Overdose is rare and mainly affects people with kidney disease. https://magnesiumguide.uk/basics/deficiency-symptoms/ https://magnesiumguide.uk/basics/deficiency-symptoms/ Wed, 04 Nov 2026 00:00:00 GMT Mild magnesium shortfall usually causes no clear symptoms. True deficiency can cause loss of appetite, nausea, tiredness and weakness, then muscle cramps, twitching, tremor, tingling, mood changes and abnormal heart rhythms. It is most often caused by long-term acid-reducing medicines, diuretics, heavy drinking, diarrhoea or poorly controlled diabetes. https://magnesiumguide.uk/forms/ https://magnesiumguide.uk/forms/ Wed, 04 Nov 2026 00:00:00 GMT For most people, magnesium citrate or glycinate is a sensible choice: both are reasonably well absorbed, and glycinate is the gentlest on the gut. Magnesium oxide holds the most magnesium per tablet but is poorly absorbed and acts as a laxative. Pricier forms such as L-threonate have little independent evidence behind their claims. https://magnesiumguide.uk/basics/ https://magnesiumguide.uk/basics/ Wed, 04 Nov 2026 00:00:00 GMT Magnesium is a mineral the body needs for more than 300 enzyme reactions, including turning food into energy, making DNA and protein, and keeping nerves, muscles and heart rhythm working normally. An adult body holds about 25 g, mostly in bone. Most people can get enough from food; some groups run short.