Magnesium Deficiency Symptoms: How to Recognise and Address Them (UK)

Ever had an eyelid that twitches for days, night‑time leg cramps that wake you up, or energy slumps you can’t quite explain? Before you doom‑scroll your way to panic, there’s a quietly common (and fixable) culprit worth checking: a lack of magnesium. This guide walks you through the signs of magnesium deficiency, what causes magnesium deficiency, what are the symptoms of magnesium deficiency, and how people in the UK can evaluate and address it—grounded in NHS, NICE and high‑quality evidence. If you want a fuller picture of supplementation, keep our pillar guide handy: Magnesium Supplements UK Guide: Evidence‑Based Benefits, Best Forms, Safe Dosage & Impact on Common Conditions.

At a glance (TL;DR)

• UK adults typically need ~300 mg/day (men) and 270 mg/day (women) of magnesium from food; doses >400 mg/day from supplements can cause diarrhoea. [1]
• The most reliable first test in UK clinical practice is a serum magnesium (Mg) blood test; a common UK reference range is ~0.70–1.00 mmol/L. [2,7]
• Early clues of a lack of magnesium include fatigue, nausea, and muscle twitches; moderate to severe deficiency can cause cramps, tingling, tremor, seizures, and heart rhythm problems—and often travels with low potassium or calcium. [2,6,9]
• Long‑term PPI use (e.g., omeprazole), diuretics, diarrhoea, alcohol misuse, diabetes, and malabsorption are frequent causes. [3,6,16,19]

1) Why magnesium matters in the UK (and how shortfalls happen)

Magnesium supports hundreds of enzymes governing energy production, nerve conduction and muscle relaxation, and healthy heart rhythm. The NHS summarises it neatly: magnesium helps turn food into energy and keeps the parathyroid glands (and therefore bone health) working normally. UK reference intakes are 300 mg/day for men and 270 mg/day for women, and the NHS advises that >400 mg/day from supplements can cause diarrhoea; ≤400 mg/day is unlikely to cause harm in most adults. [1]

Key takeaway: A lack of magnesium can show up in multiple systems—from muscle to mood to heart rhythm—so staying within the UK dietary range matters. When you search for magnesium deficiency nhs you’ll see these same fundamentals echoed. [1,2]

NDNS: how common is a shortfall?

The National Diet and Nutrition Survey (NDNS) has repeatedly flagged low magnesium intakes in several UK age‑sex groups (trend reports across years 1–9 and the combined Years 9–11 statistical summary). While the exact percentages vary by cohort and year, evidence of low intakes persists among adolescents, adults 19–64, and adults 65+. [10,11] Some mid‑life analyses also note a meaningful fraction of young adults falling below the Lower Reference Nutrient Intake (LRNI)—a level associated with higher risk of deficiency. [12]

Did you know? In the UK, intake shortfalls often cluster with dietary patterns low in wholegrains, nuts and seeds—foods richest in magnesium. Tackling a lack of magnesium usually starts with the shopping basket, not the medicine cabinet. (See food ideas below and our Magnesium UK guide)

2) “What are the symptoms of magnesium deficiency?”—from subtle to serious

Let’s answer the SEO question directly: what are the symptoms of magnesium deficiency?

• Early/subtle: low appetite, nausea, fatigue, muscle twitches (that infamous eyelid), and mild weakness. [2,9]
• Neuromuscular: muscle cramps and spasms, tremor, tetany, paraesthesias; in severe cases seizures. [6,9]
• Cardiac: palpitations or arrhythmias (e.g., prolonged QT), which can be dangerous. [6,9]
• Metabolic lab clues: hypokalaemia and/or hypocalcaemia often accompany significant hypomagnesaemia. [6,9]

These signs of magnesium deficiency rarely appear in isolation, and often depend on how low—and how fast—serum magnesium falls. The NHS also highlights cramping and arrhythmia as prompts for testing. [2,6,9]

Bottom line: If you’re noticing persistent signs of magnesium deficiency, especially with palpitations, faintness, severe cramps, or new neurological symptoms, seek medical advice promptly—don’t just self‑supplement and hope for the best. That’s straight from magnesium deficiency nhs style guidance. [2,6]

3) “What causes magnesium deficiency?”—common culprits in real life

Again, head‑on: what causes magnesium deficiency in the UK?

• Medications
  • PPIs (e.g., omeprazole) with long‑term use: the MHRA reports confirmed cases of clinically significant hypomagnesaemia—sometimes after months to a year—warranting pre‑treatment and periodic checks in at‑risk patients (especially if combined with digoxin or diuretics). [3,16,19]
  • Diuretics (loop and thiazide), some chemotherapy/EGFR inhibitors, aminoglycosides, and immunosuppressants can cause renal Mg loss. [6,9,16]
• Gastrointestinal losses & malabsorption
  • Chronic diarrhoea, IBD, coeliac disease, short bowel, vomiting, or high‑output stomas reduce absorption or increase loss. [5,6]
• Endocrine/metabolic
  • Poorly controlled diabetes (osmotic diuresis), hyperaldosteronism, alcohol misuse (low intake + renal wasting). [6,9]
• Low intake over time
  • Dietary patterns low in wholegrains, nuts/seeds and pulses lead to a lack of magnesium intake relative to UK RNIs—something NDNS repeatedly signals. [10,11,12]

Key takeaway: The single most useful question is often, “what causes magnesium deficiency *for *me?” Meds? Gut issues? Diet? Fix the cause and the signs of magnesium deficiency usually ease.

4) How do UK clinicians check magnesium levels?

Serum Mg is the starting point (and the yardstick we treat to)

In UK practice the serum magnesium test is standard. Labs commonly use 0.70–1.00 mmol/L as a reference range; replace and re‑check according to symptoms and severity. [2,7,20] Serum Mg is an imperfect mirror of total body stores—but it’s the most practical, validated clinical test and what NHS services act on. [2,7,9,20]

When to test: Per NHS guidance, test if you have symptoms such as nausea, weakness, twitching/cramping, or arrhythmia, or if you are on long‑term PPIs/diuretics or have conditions likely to cause low Mg. [2,3,16]

Beyond serum: Some specialists use 24‑hour urinary magnesium or fractional excretion of magnesium to distinguish renal wasting from GI loss when the cause isn’t obvious. [7]

Urgent care: Chest pain, syncope, marked palpitations, seizures, or severe weakness alongside worrying signs of magnesium deficiency warrant urgent assessment (999/A&E). [2,6]

5) Food first: practical ways to replete intake

Food is your safest, most sustainable fix for a lack of magnesium. UK hospital dietetic leaflets highlight wholegrains (oats, brown rice, wholemeal bread), nuts & seeds (almonds, cashews, pumpkin, sunflower), legumes, and leafy greens (spinach, kale) as staple sources. [1,20]

Bookmark for shopping inspiration: Top 10 Foods High in Magnesium – Natural Alternatives to Supplements.

At a glance: If your diet has slipped into “beige” carbs and low fibre, start by swapping in wholegrain staples and a small handful of nuts/seeds daily. That one habit makes a measurable dent in a lack of magnesium.

6) Supplements 101 (UK): who might consider them, how to choose form & dose

If diet can’t cover the gap—or you’re on a medicine that nudges magnesium down—supplements can be useful. The BNF/NICE treatment summary notes IV magnesium sulfate for symptomatic/severe cases, with oral magnesium for maintenance/prevention. There’s no single national UK guideline, but NHS Trust guidance is consistent: treat the cause, replace magnesium, and re‑check. [14,4,6,20]

• Dose: For otherwise healthy adults, keep supplemental magnesium ≤400 mg/day unless specifically advised—higher doses often cause diarrhoea. [1,6]
• Form: Citrate and glycinate are well‑tolerated for many people; oxide is economical but may be laxative. (If you’re choosing between forms, see Magnesium Citrate vs Glycinate vs L‑Threonate: Benefits, Absorption & How to Choose.)

If citrate suits you and your clinician agrees, one option is Capsure Magnesium Citrate 150 mg—a gentle‑to‑dose capsule you can space through the day.

Pro tip: For sleep or stress, see Magnesium for Sleep: Does It Reduce Stress and Improve Mood?. For leg cramps, read the evidence summary below before buying. Our comprehensive UK Guide covers dose‑timing, forms and UK safety advice.

7) Special situations, evidence & myths

Night leg cramps: temper expectations

Cochrane’s 2020 review found magnesium unlikely to reduce frequency or severity of idiopathic leg cramps in older adults; pregnancy data are conflicting. [8] If cramps are your main issue, prioritise hydration, stretching, and medication review with your GP before reaching for Mg. (If you still want to explore it, see Magnesium Citrate for Muscle Cramps & Night Leg Cramps: Evidence and Dosage (UK Guide).)

Migraine: mixed but promising in subsets

Reviews suggest magnesium may help prevent migraine (especially migraine with aura or menstrual migraine), but the quality of evidence varies, and it’s not a licensed migraine preventive in the NHS. [5,7,9] For UK‑focused practicalities, see Magnesium for Migraines UK: A Guide and keep treatments aligned with NIHR‑appraised options for chronic migraine. [5]

Blood pressure & heart health: modest effects at best

Meta‑analyses indicate small reductions in systolic/diastolic BP with magnesium supplementation, often at ≥400 mg/day, but effects are modest and heterogeneous—think of magnesium as a supporting act alongside diet, exercise, and standard care. [17,18] For the clinical nuance, see Magnesium and Blood Pressure (BP): Does Magnesium Help with High Blood Pressure, Palpitations, and Atrial Fibrillation?.

Key takeaway: When someone asks what are the symptoms of magnesium deficiency related to these conditions, remember: magnesium might play a supportive role, but it’s rarely a primary treatment.

8) Drug interactions & practical spacing (BNF‑based)

If you supplement, spacing is everything:

• Levothyroxine: magnesium (including antacids) reduces absorption. Separate by ≥4 hours. [13,14]
• Tetracyclines and some other antibiotics: avoid co‑dosing; separate by 2–3 hours to prevent chelation and reduced antibiotic levels. [13,15]
• PPIs: don’t mix with magnesium—monitor because PPIs can lower Mg over time; your GP may check Mg before/during prolonged therapy. [3,16]

Bottom line: If you’re on multiple medicines, ask your pharmacist to help map a dosing schedule. That alone can prevent an avoidable lack of magnesium or a false impression that your thyroid tablet “isn’t working.”

9) Bringing it together—how to act if you suspect a lack of magnesium

Step 1 — Sense‑check symptoms: List your signs of magnesium deficiency (twitches, cramps, fatigue, poor appetite, palpitations). Ask yourself again, what are the symptoms of magnesium deficiency you’re actually experiencing? If severe (palpitations/syncope/seizure), seek urgent care. [2,6]

Step 2 — Identify causes: Review meds and conditions (PPIs, diuretics, diabetes, diarrhoea, alcohol). This is your personalised answer to what causes magnesium deficiency. [3,6,9,16]

Step 3 — Get the right test: Ask your GP about a serum magnesium test (and labs for K⁺/Ca²⁺ if needed). The phrase magnesium deficiency nhs will take you to the official testing overview if you need a refresher before your appointment. [2,7]

Step 4 — Fix the basics:

• Food first (wholegrains, nuts/seeds, legumes, greens). [1,20]
• Consider supplements only if appropriate, keeping ≤400 mg/day from supplements unless your clinician advises otherwise. [1]
• Choose forms that suit your gut (citrate/glycinate), and space around interacting medicines. [13,14]
• For sleep timing & meals, see Best Time to Take Magnesium (UK Guide) and the full UK Guide.

10) FAQs—quick answers to long‑tail searches

Q1: What are the earliest signs of magnesium deficiency?
A: Low appetite, nausea, fatigue, eyelid twitching, and mild muscle tightness are common early signs of magnesium deficiency. If you wonder what are the symptoms of magnesium deficiency you shouldn’t ignore, add palpitations, significant cramps/spasms, or tingling. [2,9]

Q2: I take a PPI—what causes magnesium deficiency in that context?
A: PPIs can reduce intestinal magnesium absorption over months to years. The MHRA advises checking magnesium before and during prolonged PPI therapy, especially with digoxin or diuretics. [3,16]

Q3: Is a “magnesium RBC” test better?
A: In UK practice, serum magnesium drives decisions. RBC/ionised measures exist, but they’re not standardised for routine NHS care. If your clinical picture is puzzling, your team may add urine studies to distinguish renal loss from poor intake/absorption. [2,7,9]

Q4: Can magnesium help my leg cramps?
A: Evidence doesn’t show a meaningful benefit for typical idiopathic leg cramps in older adults; pregnancy data are mixed. Consider other strategies first and discuss with your GP. [8] (For a nuanced look, see our guide to magnesium citrate for night leg cramps.)

Q5: I’m plant‑based—am I at greater risk of a lack of magnesium?
A: Not necessarily; plant‑forward diets can be rich in magnesium (wholegrains, legumes, nuts, seeds). See Do Vegetarians and Vegans Need Magnesium Supplements? for meal‑based strategies.

Q6: How quickly do signs of magnesium deficiency improve?
A: Depends on the cause and severity. Mild dietary lack of magnesium may feel better within days to weeks once intake improves; drug‑induced or severe deficiency can take longer and needs medical supervision. [6,14]

Q7: How do I avoid “too much” magnesium?
A: Stick to ≤400 mg/day from supplements unless your clinician says otherwise, and be cautious with kidney disease. For a full safety run‑through, read Can You Take Too Much Magnesium? Side Effects and Warning Signs (UK). [1,6]

Final word

You don’t need to memorise biochemistry to solve a lack of magnesium. Start with your diet, scan for what causes magnesium deficiency in your life (meds, gut, intake), and get a serum magnesium test if your signs of magnesium deficiency continue. If you’re still wondering what are the symptoms of magnesium deficiency in your case—or need help navigating magnesium deficiency nhs pathways—speak to your GP or pharmacist. And for an end‑to‑end tour of supplements, bookmark our Magnesium Supplements UK Guide.

References (Vancouver)

1. National Health Service (NHS). Others: vitamins and minerals – magnesium [Internet]. 2020 Aug 3 [cited 2025 Aug 14]. Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/others/
   
   
2. NHS. Magnesium test [Internet]. 2022 May 20 [cited 2025 Aug 14]. Available from: https://www.nhs.uk/tests-and-treatments/magnesium-test/
   
   
3. Medicines and Healthcare products Regulatory Agency (MHRA). Proton pump inhibitors in long-term use: reports of hypomagnesaemia [Internet]. 2014 Dec 11 [cited 2025 Aug 14]. Available from: https://www.gov.uk/drug-safety-update/proton-pump-inhibitors-in-long-term-use-reports-of-hypomagnesaemia
   
   
4. National Institute for Health and Care Excellence (NICE). Preventing recurrent hypomagnesaemia: oral magnesium—intervention and alternatives [Internet]. 2013 Jan 29 [cited 2025 Aug 14]. Available from: https://www.nice.org.uk/advice/esuom4/chapter/intervention-and-alternatives
   
   
5. NICE. Preventing recurrent hypomagnesaemia: what is hypomagnesaemia? [Internet]. 2013 Jan 29 [cited 2025 Aug 14]. Available from: https://www.nice.org.uk/advice/esuom4/ifp/chapter/what-is-hypomagnesaemia
   
   
6. Gloucestershire Hospitals NHS Foundation Trust. Guideline for the management of hypomagnesaemia in adults [Internet]. 2021 Oct [cited 2025 Aug 14]. Available from: https://www.gloshospitals.nhs.uk/media/documents/Hypomagnesaemia_jcPg0oV.pdf
   
   
7. Royal United Hospitals Bath NHS Foundation Trust. Hypomagnesaemia – a guide for GPs [Internet]. 2024 Jun 7 [cited 2025 Aug 14]. Available from: https://www.ruh.nhs.uk/pathology/documents/clinical_guidelines/PATH-021_Hypomagnesaemia_Guideline.pdf
   
   
8. Garrison SR, Korownyk C, Kolber MR, Allan GM, Musini VM, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;9:CD009402. [Internet]. [cited 2025 Aug 14]. Available from: https://doi.org/10.1002/14651858.CD009402.pub3
   
   
9. Gragossian A, Bashir K. Hypomagnesemia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023–. [updated 2023 Nov 30; cited 2025 Aug 14]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500003/
   
   
10. Public Health England. National Diet and Nutrition Survey (NDNS): results from years 9 to 11 (2016 to 2017 and 2018 to 2019) – statistical summary [Internet]. 2020 Dec 11 [cited 2025 Aug 14]. Available from: https://www.gov.uk/government/statistics/ndns-results-from-years-9-to-11-2016-to-2017-and-2018-to-2019/ndns-results-from-years-9-to-11-combined-statistical-summary
    
    
11. Public Health England. NDNS: years 1 to 9 of the Rolling Programme (2008/09–2016/17): report [Internet]. 2019 [cited 2025 Aug 14]. Available from: https://assets.publishing.service.gov.uk/media/5c45e22340f0b61704aec504/NDNS_UK_Y1-9_report.pdf
    
    
12. Derbyshire E. Micronutrient intakes of British adults across mid-life. Nutrients. 2018;10(5):496. [Internet]. [cited 2025 Aug 14]. Available from: https://doi.org/10.3390/nu10050496
    
    
13. British National Formulary (BNF). Antacids—interactions [Internet]. [cited 2025 Aug 14]. Available from: https://bnf.nice.org.uk/interactions/antacids/
    
    
14. BNF. Levothyroxine—interactions [Internet]. [cited 2025 Aug 14]. Available from: https://bnf.nice.org.uk/interactions/levothyroxine/
    
    
15. BNF. Magnesium imbalance—treatment summary [Internet]. [cited 2025 Aug 14]. Available from: https://bnf.nice.org.uk/treatment-summaries/magnesium-imbalance/
    
    
16. NHS Dorset Integrated Care Board. The management of hypomagnesaemia in primary care [Internet]. 2023 Jan [cited 2025 Aug 14]. Available from: https://nhsdorset.nhs.uk/Downloads/aboutus/medicines-management/Other%20Guidelines/Management%20of%20hypomagnesaemia%20in%20primary%20care%20Jan%2023%20-%20Copy.pdf
    
    
17. Alharran AM, Alkhudhayri DA, Alanazi RS, Alshammari MM, Alenezi FM, et al. Impact of magnesium supplementation on blood pressure: an umbrella meta-analysis of randomised controlled trials. [Internet]. 2024 [cited 2025 Aug 14]. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11401110/
    
    
18. Zhang X, Li Y, Del Gobbo LC, Rosanoff A, Wang J, et al. Effects of magnesium supplementation on blood pressure: a meta-analysis of randomised double-blind placebo-controlled trials. Hypertension. 2016;68(2):324–333. [Internet]. [cited 2025 Aug 14]. Available from: https://doi.org/10.1161/HYPERTENSIONAHA.116.07664
    
    
19. Begley J, et al. Proton pump inhibitor–associated hypomagnesaemia: a prospective study. Eur J Gastroenterol Hepatol. 2016;28(5):[pages unavailable]. [Internet]. [cited 2025 Aug 14]. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4799921/
    
    
20. Hull University Teaching Hospitals NHS Trust. Increasing magnesium in your diet [Internet]. 2024 Jul 12 [cited 2025 Aug 14]. Available from: https://www.hey.nhs.uk/patient-leaflet/increasing-magnesium-in-your-diet/
    
    

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