How to prepare
No fasting is required. No specific preparation is needed. Take medications as normal. If the sample is left at room temperature for too long before analysis, bicarbonate can dissipate — the laboratory processes samples promptly to ensure accuracy.
After the test
Share your result with your GP alongside other electrolytes and kidney function tests. Low bicarbonate in the context of kidney disease may prompt review of diet, medication adjustments, or supplementation with bicarbonate — always under medical guidance. Significantly abnormal values require prompt clinical assessment to identify the underlying cause.
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
Bicarbonate is measured in millimoles per litre (mmol/L). The normal adult range is typically 22–29 mmol/L.
- Low bicarbonate (metabolic acidosis, below 22 mmol/L): Indicates accumulation of acid or loss of bicarbonate. Common causes include chronic kidney disease, diabetic ketoacidosis, lactic acidosis, severe diarrhoea, and renal tubular acidosis. The anion gap calculation (using sodium, chloride, and bicarbonate) distinguishes high-gap from normal-gap acidosis.
- High bicarbonate (metabolic alkalosis, above 29 mmol/L): Indicates loss of acid or excess bicarbonate retention. Common causes include prolonged vomiting, diuretic use (particularly thiazides and loop diuretics), primary hyperaldosteronism, and chronic respiratory acidosis with compensation.
- Interpretation with pH: Serum bicarbonate alone does not differentiate a primary metabolic disturbance from a compensatory response to a respiratory problem. Blood gas analysis provides this additional context when needed.
