How to prepare
No fasting is required for this test. Drink water as normal beforehand.
Let your practitioner know about any magnesium supplements you take, as these may affect results. You may be advised to stop supplementing for a period before testing. A healthcare professional will take a blood sample from a vein in your arm.
After the test
Review your result with your GP or a practitioner familiar with nutritional health. If your magnesium is low, they may investigate contributing causes and discuss whether dietary changes or supplementation are appropriate for your situation.
If serum magnesium is normal but symptoms continue, ask your practitioner about red blood cell magnesium testing, which provides a better measure of tissue-level magnesium status.
Your test results will be available in your private dashboard. If there are any urgent issues, we'll let you know so you can follow up with your health professional.
Understanding results
Results are reported in millimoles per litre (mmol/L). The reference range for adults is typically 0.70 to 1.10 mmol/L, though this varies slightly between laboratories.
Low serum magnesium (hypomagnesaemia) can be associated with muscle cramps, tremors, fatigue, irregular heart rhythms, and anxiety. Causes include poor dietary intake, alcohol use, gastrointestinal disorders, diabetes, and certain medications including diuretics and proton pump inhibitors.
High serum magnesium (hypermagnesaemia) is less common and is usually seen in people with kidney impairment or those taking large doses of magnesium-containing supplements or antacids.
Serum magnesium reflects only a fraction of total body magnesium. A normal result does not rule out tissue-level deficiency. If your result is normal but symptoms persist, your practitioner may recommend a red blood cell magnesium test for a more accurate assessment of intracellular stores.