Hypomagnesaemia (low serum magnesium: PPIs, diuretics, alcohol, diarrhoea)

Endocrinology and metabolism · Abnormal laboratory result · updated 2026-10-31

BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.

Frequency: In a general-population study in northern Serbia (5 122 adults), 2.7% had serum magnesium < 0.75 mmol/L ^[1].

Hypomagnesaemia found (< 0.7 mmol/L), without severity signs

Serum electrolytes (potassium)
Serum calcium
Serum albumin
Serum creatinine with eGFR
Fasting plasma glucose (if diabetes not known)if needednon-French guidelineDiabetes is among the causes to look for in hypomagnesaemia ^[2].
Bicarbonate (if associated hypokalaemia)if neededHypokalaemia with hypomagnesaemia: a metabolic alkalosis without digestive cause suggests diuretic intake or Gitelman syndrome ^[3].

Serum magnesium, serum creatinine, and on a urine sample taken at the same time: urinary magnesium and urinary creatinine (to calculate the fractional excretion of magnesium)if neededNo obvious cause (PPI, diuretic, alcohol, diarrhoea, diabetes): the fractional excretion of magnesium distinguishes renal loss (> 4%) from an extrarenal cause (2% or less) ^[2,3]. The urine collection must be simultaneous with the blood sample ^[3].

Detailed explanation and international comparison (in French): read it in English (machine translation)

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