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, 2} That is why 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 the things that actually lower magnesium, a diet check, and a blood test from your GP if the symptoms persist, read with the knowledge that blood magnesium is a blunt instrument.

• 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

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

1. Tiredness and weakness. Magnesium is needed to make and use energy in every cell; 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. Magnesium regulates how muscle fibres release after contracting.
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. Reported more than proven; both improve in some people whose intake was low.

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 by diet alone.

What causes low magnesium?

Four routes, often combined.^{1, 4} Not enough in. Wholegrains, nuts, seeds, pulses and green vegetables carry most dietary magnesium, and a diet built on white bread, processed food and little veg runs short; national surveys find a minority of adults and a large share of teenagers below the lower reference intake. 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. Lost in urine. Loop and thiazide diuretics, poorly controlled type 2 diabetes, heavy alcohol use and some chemotherapy and immunosuppressant drugs increase losses. More needed. Pregnancy and breastfeeding, intense training with heavy sweating, and recovery from illness. Age adds to all of them: absorption falls and medicine use rises.

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; that is why palpitations, cramps and tingling are the classic signs. The kidneys are the organ that controls magnesium, deciding how much to keep or lose, which is why kidney disease causes both deficiency and dangerous excess. Bone holds more than half 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.

What do you crave when magnesium is low?

Nothing specific, as far as anyone has shown. The chocolate story comes from the fact that cocoa is rich in magnesium, and it is repeated so often that it has become a search question, but there is no evidence that low magnesium produces a chocolate craving or any other. Cravings track habit, hunger, sleep and mood far more reliably than any single nutrient. If you crave chocolate, eat a square of the dark kind, which does contain magnesium, 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, and it is worth asking for 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 There is no reliable home test. Finger-prick kits and hair analysis sold online measure the wrong thing. The useful home check is your diet: if nuts, seeds, pulses, wholegrains and green vegetables are rare on your plate, you are probably short, and the fix is the same whether or not a test confirms it.

How to raise magnesium

Food first, because it carries the fibre, potassium and other minerals that come with it: 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 form, within the UK guidance of 400 mg for supplements, is enough to close a dietary gap; is it OK to take magnesium every day covers dose and who should not, and which magnesium is best compares the forms. Our guide to what magnesium is good for sets out its authorised roles. Expect cramps and twitching to settle over two to four weeks if magnesium was the cause; if nothing changes, it was not.

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, and the truth is a minority of adults.
• Whether supplementing people with normal blood levels helps symptoms. Trials show benefit mainly where status was low.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. 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 you check your magnesium levels at home?

No reliable home test exists. A GP blood test is the measure, with the caveat that it misses mild shortfalls; your diet is the better home check.

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. 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. PubMed 21199787.
3. Botturi A, et al. The role and the effect of magnesium in mental disorders: a systematic review. Nutrients, 2020. PubMed 32503201.
4. Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews, 2012. PubMed 22364157.

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.