Quick answer: Magnesium is a mineral essential for muscle and nerve function, heart rhythm, and bone health. The blood level is kept in a narrow range, but blood tests only show a small fraction of the body’s magnesium, so a ‘normal’ result does not always rule out a deficiency. Low magnesium is common with certain medicines (diuretics, proton-pump inhibitors), gut conditions, and alcohol use; it often travels with low potassium and low calcium.
Magnesium is easy to overlook because routine panels do not always include it — yet it underpins hundreds of body processes and its deficiency can quietly cause cramps, palpitations, and fatigue. Understanding what the blood test can and cannot tell you helps you have the right conversation with your doctor.
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Magnesium Reference Range
| Result | Interpretation |
|---|---|
| ~0.70 – 1.00 mmol/L (1.7–2.4 mg/dL) | Typical normal range (varies by lab) |
| Below range | Low — hypomagnesaemia |
| Above range | High — hypermagnesaemia, often linked to reduced kidney function |
Only about 1% of body magnesium is in the blood, so blood levels can look normal even when tissue stores are low. Always read against your lab’s range.
The Kidney Connection
The kidneys finely control magnesium — excreting excess and conserving it when needed. So when kidney function falls (a low eGFR), magnesium can build up (hypermagnesaemia), while some kidney conditions and diuretics instead cause magnesium loss. This two-way link is why magnesium is often checked alongside kidney function and other electrolytes.
Helpful for this appointment
- magnesium supplement — sometimes recommended for proven deficiency (confirm dose with your doctor)
- appointment notebook — to track symptoms and results between visits
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What Causes Low Magnesium
- Medications: diuretics, proton-pump inhibitors (long-term), some chemotherapy
- Gut conditions: chronic diarrhoea, coeliac disease, bowel resection
- Poorly controlled diabetes
- Alcohol misuse
- It often occurs with low potassium and low calcium, which can be hard to correct until magnesium is replaced
Symptoms to Mention
- Muscle cramps, twitches, or weakness
- Palpitations or irregular heartbeat
- Fatigue and low mood
- Numbness or tingling
- Nausea or poor appetite
Questions to Ask Your Doctor
- Is my magnesium low, normal, or high — and could a normal result still miss a deficiency?
- Could any of my medications be lowering it?
- Is it linked to my kidney function or other electrolytes?
- Should I take a supplement, and if so which form and dose?
- Do my potassium and calcium need checking too?
Regional Notes
Singapore: Magnesium can be added to the electrolyte panel on request; checked routinely for patients on relevant medicines or with gut conditions.
Australia: Requested by GPs when deficiency is suspected; bulk-billed or low-cost. Not always part of the default U&E.
United States: Ordered by primary care and specialists; covered by most insurers. Not part of the standard basic metabolic panel by default.
RELATED GUIDES
📊 See the full chart: compare this with typical adult ranges for common tests in our Blood Test Normal Ranges reference chart.
Medical Disclaimer: This guide is for informational and preparation purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified medical professional for guidance specific to your situation.