Magnesium
An essential mineral, and the supplement people reach for at bedtime.
- Sleep and winding down
- Stress and mood
- Migraine
- Blood pressure
- Blood sugar
A plain-English overview, not advice. Written from published reviews and trials and from what people say in public forums.
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On this page
What is magnesium?
Magnesium is a mineral the body cannot make and cannot do without. It sits behind several hundred chemical reactions, from muscle contraction and nerve signalling to a steady heartbeat, and most of us get it from green vegetables, nuts, seeds, wholegrains and beans. As a supplement it is always sold bound to something else, such as citrate, glycine or oxide, and that partner changes how much magnesium you get per tablet and how it sits in the stomach. In the UK it has become one of the most talked-about supplements of all, mostly for sleep.
Why do people take magnesium?
Sleep and winding down
The thinking. Magnesium is part of the machinery that lets muscles relax and quietens nerve signalling, so the idea is that topping up helps the body settle at night. It is the single most common reason people give for taking it, usually as glycinate in the evening, and the same muscle-relaxing role is why many people also take it for night-time cramps and twitches.
What research has found. Trials have measured how quickly people fall asleep, how long they sleep and how rested they feel. Some found modest gains, most often in older adults or people who were short of magnesium to begin with; others found no clear change, and the reviews rate the certainty of the evidence as low. Studies here point in different directions, so this one is still being worked out; the dose, how long people took it and who took part all seem to matter.
Stress and mood
The thinking. Magnesium is involved in the body’s stress response and in the chemistry that shapes mood, and low levels have been linked with feeling flat or on edge. So people take it hoping for a calmer, steadier baseline, often alongside taking it for sleep.
What research has found. A trial in adults with mild depression found lower depression scores after six weeks of magnesium. Reviews of the wider evidence on anxiety and mood found a mix of results, with the clearest hints of benefit in people who were low in magnesium or under real stress. The studies disagree, so this is unsettled: dose, duration and who took part all seem to shift the result.
Migraine
The thinking. People who get migraines are often found to have lower magnesium levels, and magnesium acts on the blood vessels and nerve signalling thought to be involved in an attack. Taking it daily in the hope of fewer attacks is a long-standing idea.
What research has found. An umbrella review, which pooled the results of many earlier reviews, found fewer and less intense migraine attacks with magnesium, and rated that among the more convincing findings for magnesium on any outcome. Research here is still young: a few studies so far, mostly pointing the same way.
Blood pressure
The thinking. Magnesium helps blood vessels relax and works alongside potassium and calcium in the balance that sets blood pressure, so a small, steady effect makes sense on paper. It is less often the reason people start taking magnesium, but it is the reason researchers have studied most.
What research has found. Four meta-analyses of randomised trials, in adults with normal or raised blood pressure, all found small average reductions in both the upper and lower readings, mostly with around 300 to 450 mg of magnesium a day. This is one of the best-studied uses, and several reviews of trials broadly agree.
Blood sugar
The thinking. Magnesium is needed for insulin to do its job, and people with type 2 diabetes are more likely to run low, so the idea is that topping up might help the body handle sugar. This is more a reason people with prediabetes or diabetes take it than a general one.
What research has found. Reviews of trials in adults with diabetes or prediabetes measured blood glucose and insulin resistance and came to different conclusions: some found improvements, others none, and a recent trial in people with insulin-treated diabetes and low magnesium found no change in insulin sensitivity. Results here go both ways, which usually means the dose, the length of a trial or the group taking part makes the difference.
What does magnesium do in the body?
Magnesium is a helper for enzymes: several hundred of the body’s chemical reactions only run when a magnesium ion is sitting in the right place. That includes the reactions that make and spend the body’s energy currency, the ones that let a muscle contract and then let go, and the ones that keep nerve signals from firing too easily. Most of the body’s magnesium is stored in bone and inside cells, with only around one per cent in the blood.
That storage pattern matters. The kidneys and gut keep blood levels steady, so a standard blood test can look normal even when stores are running low, which is one reason it is hard to know who is short of it. What a supplement adds depends on the form: the bound partner decides how much elemental magnesium is in each tablet (oxide carries the most by weight, glycinate and citrate much less) and how well it is absorbed and tolerated, which is why two products that both say “magnesium” can behave quite differently.
What do people say about taking magnesium?
These are anecdotes people have shared, not evidence.
What people like
- Deeper, steadier sleep and, above all, getting back to sleep faster after waking in the small hours. Women going through perimenopause are the most enthusiastic, and many say the clearest proof is a worse night whenever they forget a dose.
- Fewer night-time leg and calf cramps, calmer restless legs and less twitching, usually within days to a couple of weeks.
- Feeling calmer and less wired in the evening, with a quieter mind at bedtime; a few mention fewer palpitations or a stubborn eye twitch settling.
- A minority notice a brighter mood or steadier energy, though usually tangled up with other supplements taken at the same time.
Common complaints
- Loose stools, stomach cramps and urgent trips to the loo top the list, mostly with citrate and oxide, high-dose multi-form powders, or anything taken on an empty stomach. Several people switched to glycinate purely to escape this.
- A noticeable minority get the opposite of what they hoped for: worse sleep, jitteriness, a racing heart or a spike in anxiety, sometimes within a day or two.
- In every thread a handful felt no difference at all, and some are openly sceptical that the sleep effect is anything more than placebo.
- Vivid dreams and a groggy morning come up often enough to notice, as do sprays and oils that sting or itch.
How people take it
- Glycinate is the form most people suggest for sleep and a settled stomach. Citrate is seen as the cheapest but the most likely to loosen the bowels; oxide is widely written off as mainly a laxative. Malate comes up for cramps and taurate for palpitations.
- Roughly 300 to 400 mg a day, almost always in the evening after dinner or an hour before bed. The worst reactions came from multi-form powders at well over 1,000 mg a day, and the advice that follows is always to start low and build up.
- Sleep changes are typically noticed within about a week, cramps within days to a fortnight. Many say the strongest evidence came from stopping and watching the old problem return.
- People who cannot tolerate tablets move to bath flakes, sprays or a cream rubbed into the legs at bedtime. Two threads mention spacing it a few hours away from thyroid medication.
Read from these public discussions:
- Magnesium for sleep (Mumsnet, 2025)
- Magnesium?! (Mumsnet, 2023)
- To also if you take magnesium supplements (Mumsnet, 2021)
- Feel awful on Magnesium? (Mumsnet, 2025)
- Nighttime leg/calf cramps (Cronometer community forum, 2017)
What forms of magnesium are there?
| Form | What’s different | Elemental magnesium by weight | Per serving, on products we list |
|---|---|---|---|
| Bisglycinate (glycinate) | Magnesium bound to the amino acid glycine. | about 11.7 % | 85 mg to 300 mg |
| Citrate | Magnesium bound to citric acid. | about 16.0 % | 112 mg to 375 mg |
| Malate | Magnesium bound to malic acid. | about 15.5 % | not in our price tables yet |
| Taurate | Magnesium bound to taurine, an amino acid. | about 8.9 % | not in our price tables yet |
| L-threonate | Magnesium bound to threonic acid. | about 8.3 % | not in our price tables yet |
| Oxide | Magnesium bound to oxygen. | about 60.3 % | 100 mg to 300 mg |
| Chloride | Magnesium bound to chlorine; also sold as skin flakes or oil. | about 12.0 % | not in our price tables yet |
| Blends and other forms | Blends of two or more magnesium salts, or other forms. | stated on the label | 375 mg to 384 mg |
What else is worth knowing about magnesium?
- Labels give the elemental magnesium per serving, and a serving may be more than one capsule; the bound form decides how much of a tablet’s weight is actually magnesium (see the table above).
- Blood-pressure trials mostly used 300 to 450 mg of elemental magnesium a day; the mood trial ran for six weeks.
- Loose stools are the side effect trials report most, and more so with citrate and oxide; a 2026 review found no change in kidney or liver function markers.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
The research behind this page (18 studies)
- Magnesium in Prevention and Therapy. (2015, review)
- Magnesium in man: implications for health and disease. (2015, review)
- Renal control of calcium, phosphate, and magnesium homeostasis. (2015, review)
- Magnesium: Biochemistry, Nutrition, Detection, and Social Impact of Diseases Linked to Its Deficiency. (2021, review)
- Magnesium Supplementation for Sleep in Adults: A Systematic Review of Randomized Controlled Trials. (2026, systematic review)
- The Role of Magnesium in Sleep Health: a Systematic Review of Available Literature. (2023, systematic review)
- Role of magnesium supplementation in the treatment of depression: A randomized clinical trial. (2017, randomised trial)
- The Role and the Effect of Magnesium in Mental Disorders: A Systematic Review. (2020, systematic review)
- The Effects of Magnesium Supplementation on Subjective Anxiety and Stress-A Systematic Review. (2017, systematic review)
- Magnesium and health outcomes: an umbrella review of systematic reviews and meta-analyses of observational and intervention studies. (2020, meta-analysis)
- Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials. (2016, meta-analysis)
- Comprehensive Effects of Magnesium Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Dose-Response Meta-Analysis. (2026, meta-analysis)
- The effect of magnesium supplementation on blood pressure in individuals with insulin resistance, prediabetes, or noncommunicable chronic diseases: a meta-analysis of randomized controlled trials. (2017, meta-analysis)
- Effect of magnesium supplementation on blood pressure: a meta-analysis. (2012, meta-analysis)
- Effect of magnesium supplementation on glucose metabolism in people with or at risk of diabetes: a systematic review and meta-analysis of double-blind randomized controlled trials. (2016, meta-analysis)
- A systematic review and meta-analysis of randomized controlled trials on the effects of magnesium supplementation on insulin sensitivity and glucose control. (2016, meta-analysis)
- Oral magnesium supplements and insulin resistance in individuals with diabetes and pre-diabetes: an updated systematic review and meta-analysis of randomized controlled trials. (2026, systematic review)
- Oral magnesium supplementation does not affect insulin sensitivity in people with insulin-treated type 2 diabetes and a low serum magnesium: a randomised controlled trial. (2024, randomised trial)
How much does magnesium cost?
That depends on the form and the pack, so we work out the price of the same dose of every magnesium product we can find and rank them.