In short: A magnesium deficiency shows up mainly in your muscles and nerves: cramps, trembling, tiredness and exhaustion, and with a severe deficiency, an irregular heartbeat too. Common causes are too little wholegrain and nuts in your diet, heavy alcohol use, type 2 diabetes, bowel disease and acid-reducing tablets. Get persistent symptoms checked by a doctor. Diet and, if needed, a supplement can improve your magnesium intake well.
Key points
- Typical signs: muscle cramps and twitching, tiredness, exhaustion, sleep problems and irritability. A severe deficiency can throw your heart out of rhythm.
- Good to know: a mild deficiency often causes barely any symptoms, and the signs have many possible causes. That's why they belong in a doctor's hands.
- Common causes: too little magnesium in your diet, heavy alcohol use, type 2 diabetes, Crohn's disease, and long-term use of acid-reducing tablets or certain water tablets.
- Potassium is part of the picture: when magnesium is low, your body loses potassium more easily. It's worth having both checked.
- What helps: eat magnesium-rich foods (wholegrains, nuts, seeds, pulses), find the cause, and if needed, add up to 250 mg of magnesium a day from a supplement.
Contents
- What is a magnesium deficiency?
- What are the symptoms of a magnesium deficiency?
- Symptoms in women and men: is there a difference?
- What causes a magnesium deficiency?
- Magnesium and potassium deficiency: how are they linked?
- How is a magnesium deficiency diagnosed?
- Magnesium deficiency: what should you do?
- What to eat if you have a magnesium deficiency?
- Frequently asked questions
- Limits of the research and all sources
What is a magnesium deficiency?
A magnesium deficiency means your body has less magnesium available long-term than it needs. There are two possible reasons: too little comes in through food, or your body loses too much through the gut or kidneys.
It matters whether you're looking at a tight supply or a true deficiency. A tight supply means eating below your needs for weeks at a time. That's fairly common and usually goes unnoticed. A true deficiency with a low blood level is rarer and almost always has an identifiable cause, such as a medicine or an illness.
What the studies show: Your body keeps your blood magnesium level tightly between 0.7 and 1.1 mmol/l. Below that, doctors call it hypomagnesaemia.1 Because your body keeps the blood level stable by drawing on its stores, a tight supply can exist even with a normal blood level.2 Mild deficits often pass without clear signs.3
What are the symptoms of a magnesium deficiency?
The most common signs affect your muscles and nerves: cramps, trembling, muscle twitching and general exhaustion. That fits with what your body needs magnesium for. Magnesium contributes to normal muscle function. Magnesium contributes to normal functioning of the nervous system. Magnesium contributes to a reduction of tiredness and fatigue.
| Area | Possible signs | When typical |
|---|---|---|
| Muscles | muscle cramps, twitching, trembling, muscle weakness | even with a moderate deficiency |
| Energy | tiredness, exhaustion, lack of drive | common, but very non-specific |
| Mood and sleep | sleep problems, irritability, mood swings | described mainly with a mild deficiency |
| Heart | palpitations, an irregular heartbeat | with a pronounced deficiency |
| Blood levels | too little potassium and calcium in the blood | with a pronounced deficiency |
| Nervous system | seizures | rare, with a severe deficiency |
What the studies show: Medical reviews list muscle cramps, exhaustion, seizures and an irregular heartbeat as consequences of a magnesium deficiency.4 An older clinical review describes trembling and muscle twitching, and notes that a deficiency can also run its course with no noticeable symptoms at all.5 A more recent review adds muscle weakness and an irregular heart rhythm.6 With mild deficits, more general complaints such as exhaustion, sleep problems and irritability tend to be described. In older people, these are easily mistaken for signs of ageing.3 A pronounced deficiency can also lower your blood potassium and calcium levels.7
Important: These signs are not a self-test. Tiredness, cramps or sleep problems have many possible causes, from lack of sleep to your thyroid or iron levels. Get persistent symptoms checked by a doctor rather than guessing and taking a high dose. If you have heart palpitations, a racing heart or a seizure, seek medical help straight away.
Symptoms in women and men: is there a difference?
The symptoms are the same in women and men. The differences lie in how much you need and in who is more often running low.
Women need around 300 mg of magnesium a day, including during pregnancy and breastfeeding.8 In dietary data, they more often fall short relative to their needs than men do. What applies during pregnancy is covered in Magnesium in pregnancy and breastfeeding.
Men need more, at around 350 mg a day.8 If you drink alcohol regularly, it's worth paying particular attention to your magnesium intake (see Causes below). Whether athletes need more is covered in How much magnesium per day?
What the studies show: In the UK National Diet and Nutrition Survey of 3,238 adults, women scored notably lower than men, relative to the recommendation, for magnesium and eight other nutrients.9 In a Canadian study, women had lower blood magnesium levels than men; 9% of white women were below 0.75 mmol/l.10 Conversely, in US data, only 52% of men reached their average requirement from food and supplements combined.11
What causes a magnesium deficiency?
Most often, simply too little comes in through food. A true deficiency with a low blood level, however, is usually caused by losses through the gut or kidneys. Common triggers are alcohol, type 2 diabetes and certain medicines.1
| Cause | What happens | Who is affected |
|---|---|---|
| Diet | too little wholegrain, nuts, seeds, pulses, green vegetables | many adults in Europe |
| Acid-reducing tablets (proton pump inhibitors) | your gut probably absorbs less magnesium | with use over months to years |
| Water tablets (thiazide diuretics) | your kidneys excrete more magnesium | with longer-term use |
| Alcohol | more loss through the kidneys, often also too little in the diet | with regular heavy drinking |
| Type 2 diabetes | more loss through the kidneys | common, 10 to 32% depending on the study |
| Bowel disease, prolonged diarrhoea | gut absorbs less, losses through the stool | e.g. with Crohn's disease |
| Older age | less in the diet, poorer absorption, more loss | older adults |
Diet: In four European countries, average intake was 268 to 285 mg a day; only Denmark was higher.12 That's less than women (300 mg) and men (350 mg) need.8 The modern Western diet is generally considered fairly low in magnesium.2
Medicines: If you take acid-reducing tablets such as pantoprazole or omeprazole over a longer period, you're more likely to have a low magnesium level. In a population study of 9,818 people, the risk doubled, and only after longer-term use.13 In an analysis of 16 studies, 19.4% of users had a low level, compared with 13.5% of non-users.14 In reported individual cases, this appeared after 5.5 years on average, and the level recovered within a few days of stopping.15 Among water tablets, it was mainly thiazide diuretics that were linked to low levels in the same population, while loop diuretics were not.16 In hospital, certain antibiotics and cancer medicines can also cost you magnesium.17 How stomach acid affects absorption is covered in How is magnesium absorbed by the body?
Alcohol: An analysis of 25 studies found notably lower blood magnesium and less magnesium in muscle in people with chronic heavy alcohol use. The kidneys then hold on to magnesium less well.18 In a hospital study, a low magnesium level was the most common electrolyte disturbance in people with alcohol problems (29.9%).19
Type 2 diabetes: An analysis of 19 studies with 4,192 people found a low magnesium level in 32%.20 With type 2 diabetes, a low level is around ten times more common than in healthy people.21
Bowel disease: People with Crohn's disease had lower magnesium levels than healthy people in a review of eight studies; in one study, up to half were affected.22 Prolonged diarrhoea and impaired gut absorption are also classic causes.5
Age: In older age, three things often come together: less magnesium in the diet, weaker absorption in the gut, and more loss through the kidneys.3
Important: If you take acid-reducing tablets or water tablets long-term, talk to your GP about your magnesium level. Don't stop the medicine on your own. If your kidney function is reduced, the opposite applies: magnesium can then build up, and supplements should only be taken after talking to your doctor.17
Magnesium and potassium deficiency: how are they linked?
Magnesium and potassium are closely linked. When magnesium is low, your kidneys excrete more potassium. A potassium deficiency can then often only be corrected once your magnesium is right again.
Your body needs both minerals for your muscles and nerves. Potassium contributes to normal muscle function. Potassium contributes to normal functioning of the nervous system. Magnesium contributes to electrolyte balance. If you have cramps, muscle weakness or heart palpitations, it's worth having both levels checked.
What the studies show: When magnesium inside cells falls, certain potassium channels in the kidney open more, and more potassium is lost.23 In people with a potassium deficiency, magnesium is also low in 38 to 42% of cases.24 In a population study, thiazide water tablets were linked to both low potassium and low magnesium.25
How is a magnesium deficiency diagnosed?
The usual route is a blood test at your GP's. It measures the magnesium level in your blood serum. Below 0.7 mmol/l, a deficiency is very likely.1
A normal level, though, doesn't reliably rule out a tight supply, because the blood level doesn't accurately reflect your body's stores.2 That's why doctors look at the blood level together with your symptoms, medicines and diet. A low blood level does fit well with the presence of symptoms.17 You can't reliably check this yourself at home: whether a true deficiency is present is only shown by a blood test together with a conversation with your doctor.
Magnesium deficiency: what should you do?
With a tight supply, a more magnesium-rich diet is usually enough, supplemented with a product if needed. With a true deficiency, your doctor identifies the cause and decides how much you should take.
How to do it in practice:
- Check your plate: do you eat wholegrains, nuts or seeds daily, and pulses or green vegetables several times a week? If not, you're probably below your needs. How much you need is covered in How much magnesium per day?
- Find the cause: raise medicines, alcohol, diabetes or bowel symptoms at your doctor's appointment.
- Supplement in a targeted way: up to 250 mg of magnesium a day from a supplement is considered safe.26 It's best taken with a meal.
- Be patient: give a change a few weeks before judging the results.
What the studies show: An analysis of 48 controlled studies shows that magnesium from supplements reliably raises blood levels. The level rises with the amount and the duration, reaching a stable plateau after around 20 weeks. The blood level responded most strongly in people who started out low.27
More magnesium doesn't automatically help more. From around 250 mg from supplements, loose stools and diarrhoea become more common.26 Where the limits lie is covered in Too much magnesium
Our take: magnesium is worthwhile above all where a deficiency is likely. That applies with a magnesium-poor diet and long-term medicines such as acid-reducing tablets. It applies equally with type 2 diabetes, heavy alcohol use, bowel disease and older age. For these groups, it makes sense to have your level checked and to improve your intake in a targeted way, through food and a moderate supplement. Whether magnesium also helps with calf cramps without a proven deficiency is something further studies still need to clarify (more under "Limits of the research").
What to eat if you have a magnesium deficiency?
Go for foods from seeds and leaves: wholegrain bread and porridge oats, pumpkin and sunflower seeds, almonds and cashews, beans and lentils, and leafy greens such as spinach and chard. Magnesium-rich mineral water counts too.
What the studies show: leafy greens, wholegrains, nuts, seeds and pulses are considered particularly rich magnesium sources.6 You'll find the full table with milligrams per portion in Magnesium-rich foods
Frequently asked questions
What are the typical symptoms of a magnesium deficiency? Most often muscle cramps, twitching, trembling, tiredness and exhaustion, plus sleep problems and irritability. With a pronounced deficiency, an irregular heartbeat and seizures can occur too.4, 5 All of these signs also have other causes.
How quickly can a magnesium deficiency be corrected? That depends on the cause. In studies using supplements, the blood level rose over several weeks and was stable after around 20 weeks.27 A deficiency caused by acid-reducing tablets resolved, in reported individual cases, within a few days of stopping, but that decision should only be made by your doctor.15
Can I tell if I have a magnesium deficiency myself? Not reliably. Your diet gives a good clue as to whether you're running low. Whether a true deficiency is present can only be shown by a blood test together with a conversation with your doctor.
Magnesium deficiency vs vitamin B12 deficiency: how do the symptoms differ? Both can make you tired, so the symptoms alone don't tell them apart. Magnesium contributes to a reduction of tiredness and fatigue. Vitamin B12 contributes to the reduction of tiredness and fatigue. With persistent tiredness, it's best to have both levels checked in your blood.
Is a magnesium deficiency dangerous? A tight supply is common and can usually be corrected well through diet. A pronounced deficiency with a low blood level, however, belongs in medical care, because it can affect your heart and nerves.4
What helps with a magnesium deficiency? Magnesium-rich foods and mineral water are the simplest starting point. A supplement with up to 250 mg of magnesium a day can top up your intake.26 What magnesium is needed for in your body overall is covered in Magnesium benefits: what it does in your body
Limits of the research and all sources
There's still no simple, precise test for magnesium status. The blood level captures only a small part of the magnesium in your body, and experts don't agree exactly where a deficiency begins.2, 17 The figures on medicines, alcohol and diabetes come from observational studies. They show associations, not proof of cause and effect in every case. With type 2 diabetes, the proportions vary widely: in a Dutch group of 929 GP patients, the figure was 9.6%, well below the figure from the pooled analysis.28 The data on women and men come from the UK, Canada and the US.
For calf cramps without a proven deficiency, magnesium has so far shown little benefit in studies. A Cochrane review of 11 studies found no meaningful difference from placebo in older people with night-time calf cramps.29 A study of 94 participants using magnesium oxide reached the same result.30 A study of 175 participants, by contrast, found fewer and shorter cramps than with placebo; it was funded by the manufacturer of the product tested.31 How well magnesium works for cramps when a deficiency is actually present has barely been studied directly.
Show all 31 sources
| # | Study | Who was studied | Result | Strength of evidence |
|---|---|---|---|---|
| 1 | Kröse & de Baaij 2024, Nephrol Dial Transplant | Review | blood level 0.7 to 1.1 mmol/l; common causes of low levels: alcohol, type 2 diabetes, acid-reducing tablets, thiazides | review, publicly funded |
| 2 | Fiorentini et al. 2021, Nutrients | Review | blood level doesn't reliably reflect body stores; Western diet often low in magnesium | review |
| 3 | Barbagallo et al. 2021, Nutrients | Review | mild deficits often without clear signs; exhaustion, sleep problems, irritability; in older age less intake and absorption, more loss | review |
| 4 | Bosman et al. 2021, Proc Nutr Soc | Review | deficiency: muscle cramps, exhaustion, seizures, irregular heartbeat | review |
| 5 | Flink 1981, Acta Med Scand Suppl | Clinical review | trembling, muscle twitching, irregular heartbeat; deficiency possible without symptoms; causes: gut, diuretics, alcohol | older standard review |
| 6 | Fatima et al. 2024, Cureus | Review | muscle weakness, tiredness, trembling, irregular heartbeat; sources: leafy greens, wholegrains, nuts, seeds, pulses | review |
| 7 | Hansen & Bruserud 2018, J Intensive Care | Review, intensive-care patients | deficiency can lead to low potassium and calcium | review |
| 8 | EFSA 2015, EFSA J | Official opinion | adequate intake: men 350 mg, women 300 mg; no extra need in pregnancy | official assessment |
| 9 | Derbyshire 2018, Front Nutr | 3,238 adults, UK dietary survey | women lower than men relative to the recommendation for 9 nutrients incl. magnesium | analysis of a population survey |
| 10 | Bertinato et al. 2015, Food Nutr Res | 591 adults in Canada | women with lower blood level; 9% of white women below 0.75 mmol/l | cross-sectional study |
| 11 | Omofuma et al. 2024, J Acad Nutr Diet | 35,037 adults, US dietary survey | 52% of men reach the average requirement from food and supplements | analysis of a population survey |
| 12 | Mertens et al. 2019, Eur J Nutr | Dietary surveys from 4 EU countries | magnesium intake 268 to 285 mg/day, except Denmark | comparison of national surveys |
| 13 | Kieboom et al. 2015, Am J Kidney Dis | 9,818 people, Rotterdam Study | acid-reducing tablets: double the risk of a low level, only with longer-term use | population study |
| 14 | Srinutta et al. 2019, Medicine | 16 observational studies, 131,507 people | low level in 19.4% of users, 13.5% of non-users | meta-analysis |
| 15 | Hess et al. 2012, Aliment Pharmacol Ther | Published case reports | onset after 5.5 years on average; recovery after stopping in around 4 days | systematic review of cases |
| 16 | Kieboom et al. 2018, Pharmacoepidemiol Drug Saf | 9,820 people, Rotterdam Study | thiazides: around three times the risk; loop diuretics not | population study |
| 17 | Rosner et al. 2023, Mayo Clin Proc | Review | causes incl. antibiotics and cancer medicines; blood level a weak measure, but fits with symptoms; build-up with reduced kidney function | review |
| 18 | Vanoni et al. 2021, Nutrients | 25 studies | lower blood and muscle levels with chronic heavy alcohol use; kidneys retain magnesium less well | meta-analysis, highly heterogeneous studies |
| 19 | Elisaf et al. 1995, J Trace Elem Med Biol | 127 hospital patients with alcohol problems | low level in 29.9%, most common electrolyte disturbance | observational study |
| 20 | Pitliya et al. 2024, Endocrine | 19 studies, 4,192 people with type 2 diabetes | low level in 32% | meta-analysis of observational studies |
| 21 | Oost et al. 2023, Endocr Rev | Review | low level around ten times more common with type 2 diabetes than in healthy people | review |
| 22 | Costescu et al. 2024, Nutrients | 8 studies, 453 patients with Crohn's disease | lower blood levels than healthy people; up to 50% affected in one study | systematic review |
| 23 | Huang & Kuo 2007, J Am Soc Nephrol | Review | magnesium deficiency increases potassium loss via the kidney | review |
| 24 | Whang et al. 1992, Arch Intern Med | Review | magnesium deficiency alongside potassium deficiency in 38 to 42% of cases | review |
| 25 | Liamis et al. 2013, Am J Med | 5,179 people aged 55+, Rotterdam Study | thiazides linked with both low potassium and low magnesium | population study |
| 26 | SCF 2001 / EFSA 2006 | Official opinion | upper limit 250 mg/day from supplements; loose stools the main side effect | official assessment |
| 27 | Zhang et al. 2016, J Nutr | 48 controlled studies, 2,131 people | supplements raise the blood level; stable after around 20 weeks; stronger with a low starting level | meta-analysis |
| 28 | Waanders et al. 2020, Endocrine | 929 GP patients with type 2 diabetes, Netherlands | low level in 9.6% | observational study |
| 29 | Garrison et al. 2020, Cochrane Database Syst Rev | 11 studies, 735 people | no meaningful difference from placebo in older people with calf cramps; mixed results in pregnancy | systematic review |
| 30 | Roguin Maor et al. 2017, JAMA Intern Med | 94 adults with night-time calf cramps, magnesium oxide, 4 weeks | not better than placebo | controlled study |
| 31 | Barna et al. 2021, Nutr J | 175 adults with night-time calf cramps, 60 days | fewer and shorter cramps than with placebo | controlled study, funded by the manufacturer of the product |
Author: PRONESIUM Editorial Team · Last reviewed: 01/10/2026 · This article does not replace medical advice.
