Acid-BaseUpdated 2025-12-24Medically Reviewed
Bicarbonate (HCO₃⁻)
Everything you need to know about Bicarbonate (HCO₃⁻) levels, including what normal ranges look like and what abnormal results might indicate.
Standard Reference Range
Unit: mmol/LMale Reference Range
22–29 mmol/L
Female Reference Range
22–29 mmol/L
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Reference ranges may vary slightly between laboratories. Always consult your doctor for interpretation.
What is Bicarbonate?
Bicarbonate (HCO₃⁻) is the main buffer that keeps blood pH stable. On basic metabolic panels it appears as “CO₂”.
Key Takeaway
Low bicarbonate points to metabolic acidosis; high suggests metabolic alkalosis or CO₂ retention.
Why is this test performed?
- Evaluate acid-base status in kidney, lung, or metabolic disorders
- Monitor patients on diuretics or with dehydration
- Assess diabetic ketoacidosis severity
Interpreting Your Results
- Low (＜22): Metabolic acidosis (DKA, renal failure, diarrhea), compensated respiratory alkalosis
- High (＞29): Metabolic alkalosis (vomiting, diuretics), compensated respiratory acidosis (COPD)
Related Tests
- Anion Gap / Chloride / Sodium / Potassium: Needed to classify acidosis/alkalosis
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