What Are the Signs of Low Magnesium? The 7 Signs and the Myths

The signs of low magnesium are tiredness and weakness, muscle cramps and twitching, numbness or tingling, nausea and a poor appetite, and, when it is severe, an irregular heartbeat, personality change or seizures. Those are the recognised symptoms of magnesium deficiency, and the first few are so common and so non-specific that they are also the signs of low iron, low vitamin D, an underactive thyroid, poor sleep and stress.^{1, 8} So the "seven signs your body needs magnesium" videos are right about the list and wrong about the conclusion: the list cannot tell you that magnesium is the cause. What can is a look at what actually lowers magnesium, a diet check, and a GP blood test if symptoms persist, read knowing that blood magnesium is a blunt instrument. For the sleep question itself: does low magnesium affect sleep?

• Early signs: tiredness, weakness, muscle cramps and twitching (including eyelid twitch), numbness and tingling, nausea, poor appetite
• Severe signs: irregular heartbeat, low calcium and potassium, personality change, seizures; medical, not a supplement decision
• What lowers magnesium: a diet low in wholegrains, nuts, seeds, pulses and greens; alcohol; diarrhoea and gut disease; type 2 diabetes; acid-suppressing medicines and diuretics; older age
• Myths: craving chocolate, "90% of people are deficient", home tests
• Test: a GP blood test, which under-reads mild shortfalls because less than 1% of the body's magnesium is in the blood

Sources checked on 29 October 2026.

The 7 signs your body may need magnesium

These are the recognised features of hypomagnesaemia, the medical term for low blood magnesium, in roughly the order they appear.^{1, 8}

1. Tiredness and weakness. The first sign of shortfall is a flat, heavy fatigue that sleep does not fix.
2. Muscle cramps, twitches and spasms. Night cramps in the calves, a twitching eyelid, restless legs.
3. Numbness and tingling. Usually in the hands, feet or around the mouth, from altered nerve signalling.
4. Nausea, vomiting and loss of appetite. Early and easily blamed on something else.
5. Low mood, irritability or feeling anxious. Magnesium contributes to normal psychological function; low status is linked with worse mood in population studies, though trials of supplements are mixed.³
6. Palpitations or an irregular heartbeat. A sign of more marked deficiency, because the heart's rhythm depends on magnesium, potassium and calcium together. New palpitations need a GP, not a supplement.
7. Headaches and poor sleep. Three small trials in 151 older adults, pooled, found they fell asleep about 17 minutes sooner on low-quality evidence, and no sleep claim is authorised; for migraine, one 81-person trial of 600 mg a day for 12 weeks cut attacks, with diarrhoea in one in five, and there is no UK claim.^{9, 10}

Severe deficiency adds personality change, seizures and dangerously low calcium and potassium that will not correct until magnesium does; that picture belongs in hospital and is almost always caused by illness or medicines, not diet alone.

What causes low magnesium?

Three routes, often combined.^{1, 4, 8} Not enough in. Wholegrains, nuts, seeds, pulses and green vegetables carry most dietary magnesium, and a diet of white bread, processed food and little veg runs short; the national diet survey for 2019 to 2023 found 17% of adults aged 19 to 64 and 39% of 11 to 18 year olds below the lower reference intake.¹¹ Not absorbed. Coeliac disease, Crohn's disease, chronic diarrhoea, bowel surgery and long-term use of acid-suppressing medicines such as omeprazole all reduce uptake; the medicines regulator has warned about low magnesium on proton pump inhibitors taken for more than a year.¹² Lost in urine. Loop and thiazide diuretics, poorly controlled type 2 diabetes, heavy alcohol use and some chemotherapy and immunosuppressant drugs increase losses. Age adds to all of them, because medicine use rises.¹

Over months, a measurably low magnesium can bring persistent cramps and twitching, fatigue and, when severe, seizures and heart-rhythm disturbances; it also keeps blood calcium and potassium low until it is corrected.^{5, 8}

What organ is most affected by low magnesium?

The heart and the nervous system, because both depend on the balance of magnesium, potassium and calcium across cell membranes, hence palpitations, cramps and tingling. The kidneys are the organ that controls magnesium, which is why kidney disease causes both deficiency and dangerous excess. Bone holds 50 to 60% of the body's magnesium and acts as the reserve, releasing it slowly when intake falls, which is also why blood levels stay normal until the reserve is well down.¹

What do you crave when magnesium is low?

Nothing specific. The chocolate story comes from cocoa being rich in magnesium; there is no evidence that low magnesium produces a chocolate craving or any other. Eat a square of dark chocolate if you like it, and do not read it as a diagnosis.

How do you check magnesium levels, and can you do it at home?

Your GP can test serum magnesium; ask if symptoms persist, particularly if you take a diuretic or a proton pump inhibitor, have diabetes or a gut condition, or drink heavily. The caveat is that less than 1% of the body's magnesium circulates in the blood and the body defends that level by drawing on bone, so a normal result does not rule out a modest dietary shortfall; a low result is always meaningful.^{4, 6} There is no reliable home test; a 2018 review found the common assays make magnesium status hard to determine.⁷ The useful home check is your diet: if nuts, seeds, pulses, wholegrains and green vegetables are rare on your plate, you are probably short.

How to raise magnesium

Food first: a small handful of pumpkin seeds or almonds a day, oats or wholegrain bread instead of white, beans or lentils a few times a week, spinach or chard, a square of dark chocolate. Which foods contain magnesium gives the figures per portion. Cut back on alcohol. If a supplement makes sense, 100 to 300 mg of elemental magnesium a day in a plain salt, within the UK guidance of 400 mg for supplements, is enough to close a dietary gap; the figure to read on a label is elemental magnesium per serving.¹³ Is it OK to take magnesium every day covers dose and who should not, which magnesium is best compares the forms, and what magnesium is good for sets out the authorised roles. If cramps and twitching have not changed after a month, look for another cause with your GP.

When to see a doctor

New or persistent palpitations or an irregular heartbeat; numbness or tingling that spreads or persists; muscle twitching with weakness; seizures; severe or persistent cramps; symptoms alongside a diuretic, a proton pump inhibitor, diabetes, a gut condition or heavy drinking. These need a blood test and a cause, not a supplement. Anyone with kidney disease should not take magnesium without medical advice.

What we don't know

• How common mild shortfall is. Blood tests under-read it and intake surveys over-simplify it; "90% deficient" has no source; the 2019 to 2023 national survey put 17% of adults below the lower reference intake.¹¹
• Whether supplementing people with normal blood levels helps symptoms. Trials show benefit mainly where status was low, and because a blood test under-reads a dietary shortfall, a normal result does not mean there is no gap to close.^{2, 3}
• Whether cravings relate to magnesium at all. No evidence either way.

Frequently asked questions

What are the first signs of low magnesium?

Tiredness, weakness, muscle cramps or twitching, tingling, nausea and poor appetite. All are non-specific, so look at causes and diet before blaming magnesium.¹

What hurts when your magnesium is low?

Muscles: cramps in the calves and feet, especially at night, and twitching or spasms.⁸ Headaches are reported too. Bone and joint pain are not typical.

What depletes magnesium the most?

Heavy alcohol use, chronic diarrhoea or gut disease, long-term proton pump inhibitors, loop and thiazide diuretics, and poorly controlled diabetes, on top of a low-magnesium diet.⁴

Can low magnesium be dangerous?

Severe low magnesium can cause seizures and heart-rhythm disturbances and needs medical treatment; mild shortfall from diet does not.⁵ A serum test is a reasonable check that can miss a mild shortfall; a low result is always meaningful.⁶ The "45% of people are deficient" figure online is a US estimate from an industry-authored review.⁷

Does low magnesium cause heart palpitations?

It can, when deficiency is marked. New palpitations need a GP and a blood test rather than a supplement, and anyone with a diagnosed heart rhythm condition should ask their cardiologist before taking magnesium.

Sources

1. Liamis G, et al. An overview of diagnosis and management of drug-induced hypomagnesemia. Pharmacology Research and Perspectives, 2021. Narrative review; no conflicts declared; funding not stated on PubMed. PubMed 34278747.
2. Nielsen FH, Johnson LK, Zeng H. Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnesium Research, 2010. Randomised placebo-controlled trial, 100 adults over 51, 320 mg a day for 7 weeks; funding not stated on PubMed. PubMed 21199787.
3. Botturi A, et al. The role and the effect of magnesium in mental disorders: a systematic review. Nutrients, 2020. Systematic review, 32 studies; authors declare no conflict; funding not stated on PubMed. PubMed 32503201.
4. Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews, 2012. Narrative review of US data; authors at a magnesium research centre; funding not stated on PubMed. PubMed 22364157.
5. Bosman W, Hoenderop JGJ, de Baaij JHF. Genetic and drug-induced hypomagnesemia: different cause, same mechanism. Proceedings of the Nutrition Society, 2021. Narrative review; funding not stated on PubMed. PubMed 33906702.
6. Jahnen-Dechent W, Ketteler M. Magnesium basics. Clinical Kidney Journal, 2012. Narrative review; funding not stated on PubMed. PubMed 26069819.
7. Workinger JL, Doyle RP, Bortz J. Challenges in the diagnosis of magnesium status. Nutrients, 2018. Narrative review; two authors employed by an ingredient supplier and one a paid consultant to it. PubMed 30200431.
8. Gröber U, Schmidt J, Kisters K. Magnesium in prevention and therapy. Nutrients, 2015. Narrative review; funding not stated on PubMed. PubMed 26404370.
9. Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies, 2021. Pooled analysis, 3 randomised trials, 151 older adults; no conflicts declared; funding not stated on PubMed. PubMed 33865376.
10. Peikert A, Wilimzig C, Köhne-Volland R. Prophylaxis of migraine with oral magnesium: results from a prospective, multi-center, placebo-controlled and double-blind randomized study. Cephalalgia, 1996. Randomised placebo-controlled trial, 81 adults, 12 weeks; funding not stated on PubMed. PubMed 8792038.
11. National Diet and Nutrition Survey 2019 to 2023: data table 5.41, magnesium. Published 11 June 2025. gov.uk.
12. MHRA. Proton pump inhibitors in long-term use: reports of hypomagnesaemia. Drug Safety Update, published on gov.uk 11 December 2014. gov.uk.
13. NHS. Vitamins and minerals: others, including magnesium. Page last reviewed 3 August 2020 (review overdue). nhs.uk.

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This article is general information, not medical advice. Palpitations, spreading numbness, seizures or persistent cramps need a GP; do not take magnesium supplements with kidney disease without medical advice.