Low or high bicarbonate (total CO2) on serum electrolytes

Nephrology · Abnormal laboratory result · updated 2026-10-31

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

Frequency: Among patients with chronic kidney disease followed in France (NephroTest cohort), bicarbonate is low (metabolic acidosis) in 2% of patients with a measured GFR of 60 to 90 mL/min/1.73 m², up to 39% below 20 mL/min/1.73 m² ^[1]; in a large population database, the prevalence of bicarbonate < 22 mmol/L is about 7% at stage G3A1, and 36 to 38% at stage G5A3 ^[2]. No figure found for the general French population.

Low bicarbonate (< 22 mmol/L)

Laboratory tests

Full serum electrolytes (sodium, potassium, chloride, bicarbonate, protein): anion gap calculation
Serum creatinine with eGFR
Plasma glucose
Urine dipstick in the practice (ketonuria, glycosuria), if diabetes or treatment with a gliflozinif neededPatient with diabetes, especially on a gliflozin (SGLT2 inhibitor): ketoacidosis must be looked for in the presence of symptoms, even non-specific ones, whatever the blood glucose (sometimes < 14 mmol/L) ^[3].

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

High bicarbonate (> 30 mmol/L)

Laboratory tests

Full serum electrolytes (sodium, potassium, chloride, bicarbonate, protein)
Serum creatinine with eGFR
Serum magnesium
Serum calciumif needednon-French guidelineCalcium intake (osteoporosis, heartburn) or alkali intake: milk-alkali syndrome combines PTH-independent hypercalcaemia, metabolic alkalosis and impaired renal function ^[8].
Serum albuminif needednon-French guidelineCalcium intake (osteoporosis, heartburn) or alkali intake: milk-alkali syndrome combines PTH-independent hypercalcaemia, metabolic alkalosis and impaired renal function ^[8].

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

Sources (13)