Bicarbonate (CO2)
The blood's main buffer, keeping its acidity in a tight, safe range. Measured as part of the electrolyte panel, a low or high level signals an acid-base disturbance from the kidneys, lungs, gut or metabolism rather than a problem in itself.
What it measures
Bicarbonate (often reported as 'total CO2') is the body's principal buffer against acid. The lungs and kidneys work together to keep blood acidity (pH) in a narrow range, and bicarbonate is the metabolic half of that system — the kidneys raise or lower it to compensate for acid loads. It is measured as part of the routine electrolyte panel alongside sodium, potassium and chloride, and it is interpreted with the anion gap (calculated from the electrolytes) to work out the cause of any disturbance. A low bicarbonate means metabolic acidosis (too much acid), a high one means metabolic alkalosis (too little acid) — each with its own set of causes. On its own it is a clue, not a diagnosis; the pattern with the other electrolytes and the clinical picture tells the story.
What a high value can mean
- Metabolic alkalosis — the general meaning.
- Vomiting or loss of stomach acid — a common cause.
- Diuretics — potassium and hydrogen loss.
- Low potassium, some hormonal conditions (including primary aldosteronism, Cushing's).
- Compensation for chronic lung disease — the kidney retains bicarbonate to offset retained CO2.
What a low value can mean
- Metabolic acidosis — the general meaning; interpreted with the anion gap.
- High-anion-gap acidosis — diabetic ketoacidosis, lactic acidosis, kidney failure, certain poisonings.
- Normal-anion-gap acidosis — diarrhoea (bicarbonate loss), some kidney tubular disorders.
- Compensation for over-breathing (respiratory alkalosis).
When to discuss with a doctor
Bicarbonate is read as part of the electrolyte and acid-base picture, not alone — its value is in flagging a disturbance and, with the anion gap, pointing toward the cause. A low bicarbonate with a high anion gap can signal something acute and serious, such as diabetic ketoacidosis or lactic acidosis, and in an unwell person needs urgent assessment. A persistently low bicarbonate can reflect chronic kidney disease. A high bicarbonate usually reflects fluid, potassium or acid loss. Mediora.AI shows bicarbonate with the other electrolytes and, where possible, the anion gap so the acid-base pattern is read together; the clinical interpretation belongs with your doctor.