Signs of Magnesium Deficiency: What to Look For and What to Do
The signs of magnesium deficiency, who is most at risk, how it is tested and what the NHS says about safe supplement doses. GUUDIES contains no magnesium.
By the GUUDIES Editorial Team · Updated 26 October 2026 · Claims checked against the GB Nutrition and Health Claims Register; sources below.
Disclosure: GUUDIES sells a daily gummy pouch. It contains no magnesium, so nothing in this guide is a reason to buy it for low magnesium.
The short answer: the signs of magnesium deficiency are vague at first (loss of appetite, nausea, tiredness and weakness) and, if levels keep falling, can include numbness, tingling, muscle cramps, an irregular heartbeat and, in severe cases, seizures. Because these signs overlap with many other conditions, a GP and a blood test are the way to find out, not a symptom checklist.
What Does Magnesium Do?
Magnesium is a mineral found in a wide range of foods, including spinach, nuts and wholemeal bread (NHS). In Great Britain, the authorised health claims say that magnesium contributes to the reduction of tiredness and fatigue, to normal muscle function and to normal psychological function. The NHS says adults aged 19 to 64 need about 300mg a day (men) and 270mg a day (women), and most people can get this from a varied diet.
Signs of Magnesium Deficiency
The US National Institutes of Health describes the signs in stages (NIH ODS). It also notes that symptomatic deficiency from a low intake alone is uncommon in healthy people, because the kidneys hold on to magnesium when intake is low.
| Stage | Possible signs | What else could cause them |
|---|---|---|
| Early | Loss of appetite, nausea, vomiting, tiredness, weakness | Infections, poor sleep, stress, low iron, thyroid problems and much more |
| Progressing | Numbness, tingling, muscle cramps or spasms, personality changes | Low calcium or potassium, nerve problems, dehydration |
| Severe | Abnormal heart rhythms, seizures | Needs urgent medical assessment whatever the cause |
NHS clinical guidance used by GPs notes that most people with low magnesium have no symptoms at all, and that symptoms usually appear only when blood levels are quite low (NHS BNSSG Remedy). Low magnesium also often travels with low calcium or low potassium, which can cause similar symptoms.
If you have chest pain, a racing or irregular heartbeat, fainting or a seizure, seek urgent medical help rather than trying a supplement.
Who Is More Likely to Have Low Magnesium?
Low magnesium is much more often linked to a medical condition or medicine than to diet alone. The groups at higher risk include (NIH ODS; NHS BNSSG Remedy):
- Gut conditions: Crohn's disease, coeliac disease, long-term diarrhoea or previous bowel surgery.
- Type 2 diabetes: more magnesium can be lost in urine.
- Regular heavy drinking: lower intake and higher losses.
- Older adults: tend to eat less magnesium and absorb less of it.
- Some medicines: long-term proton pump inhibitors (such as omeprazole), loop and thiazide diuretics, and certain other prescription medicines.
If you are in one of these groups and recognise the signs above, mention magnesium to your GP or pharmacist.
Can a Blood Test Show Magnesium Deficiency?
A standard blood test measures serum magnesium, and it is the usual starting point. It has a known limit: less than 1% of the body's magnesium is in the blood, and the rest is mostly in bone and soft tissue (NIH ODS). The body keeps blood levels in a tight range, so a normal result does not always reflect total stores. That is why doctors look at the test alongside your symptoms, medicines and other results, such as calcium and potassium. It is not a reason to skip the test and guess.
What to Do If You Think You Are Low
- See your GP if symptoms are new, persistent or getting worse, especially if you take any of the medicines above.
- Look at your diet: green leafy vegetables, nuts, seeds, wholegrains and pulses all contain magnesium.
- If you choose a supplement, the NHS says having 400mg or less a day of magnesium from supplements is unlikely to cause any harm, and that more than 400mg for a short time can cause diarrhoea (NHS).
- Check interactions: magnesium can reduce the absorption of some antibiotics (tetracyclines and quinolones) and osteoporosis medicines (bisphosphonates), so timing matters. Ask your pharmacist.
- Do not self-manage severe symptoms. Very low magnesium is a medical problem, and doctors may give it by drip in hospital.
If you are pregnant, breastfeeding, have kidney disease, or take regular medication, speak to your GP or pharmacist before taking magnesium.
Which Form of Magnesium?
Supplements use different magnesium compounds, such as citrate, glycinate and oxide. Forms that dissolve well in liquid tend to be absorbed more completely, and citrate is among the forms reported to be better absorbed than oxide (NIH ODS). Always compare the amount of elemental magnesium on the label, not the weight of the compound. Our guide to magnesium glycinate vs citrate goes into more detail.
Where GUUDIES Fits
GUUDIES contains no magnesium. If you need magnesium, take a separate magnesium product and check the dose with your pharmacist.
GUUDIES is one daily pouch of six pectin-based gummies for adults. The Daily Greens+ gummy carries 14 vitamins and minerals, including vitamin B6 (1.7mg) and vitamin B12 (24µg). Vitamins B6 and B12 contribute to the reduction of tiredness and fatigue and to normal psychological function. That is not a substitute for magnesium, and it will not correct a magnesium deficiency. Five of the six gummies are vegan; Marine Collagen contains fish. Every ingredient and dose is listed on our ingredients page.
Common Questions
What are the first signs of magnesium deficiency?
Early signs are non-specific: loss of appetite, nausea, vomiting, tiredness and weakness. Many people with low magnesium have no symptoms at all.
Can low magnesium cause muscle cramps?
Yes, muscle cramps and spasms can be a sign as levels fall, but cramps have many other causes. A GP can check magnesium, calcium and potassium together.
How do I know if I am magnesium deficient?
Only a doctor can tell you, usually with a blood test plus a look at your symptoms and medicines. Symptoms alone are not enough to diagnose it.
How much magnesium is safe to take as a supplement?
The NHS says 400mg or less a day from supplements is unlikely to cause harm. Higher doses can cause diarrhoea.
Does GUUDIES contain magnesium?
No. GUUDIES contains no magnesium, so take a separate product if you need it.
Sources
- NHS, Vitamins and minerals: Others (magnesium): nhs.uk
- NIH Office of Dietary Supplements, Magnesium fact sheet for health professionals: ods.od.nih.gov
- NHS Bristol, North Somerset and South Gloucestershire, Remedy: Hypomagnesaemia: remedy.bnssg.icb.nhs.uk
- GB Nutrition and Health Claims Register: gov.uk
Related Reading
Magnesium Glycinate vs Citrate · Magnesium Gummies UK Guide · Tiredness Supplements and Causes · GUUDIES ingredients
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