Lab test glossary · Other
Bicarbonate (CO₂): what it means
Also known as: CO2, total CO2, HCO3
Bicarbonate reflects your body's acid-base balance; abnormal levels point toward breathing, kidney, or metabolic causes.
What it measures
The CO₂ (bicarbonate) on a metabolic panel is a measure of how much bicarbonate is in your blood, which reflects your acid-base balance. Your lungs and kidneys work together to keep it steady, so an abnormal value is a clue that one of those systems — or your metabolism — is off.
Typical range
Often roughly 22–29 mmol/L.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Vomiting or dehydration
- Some lung conditions
- Certain diuretics
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Kidney conditions
- Uncontrolled diabetes (ketoacidosis)
- Severe diarrhea
Why the trend matters
Bicarbonate is interpreted with the rest of your electrolytes and your clinical picture; the trend helps separate a transient shift from a persistent one.
When to talk to your doctor
Discuss a clearly abnormal bicarbonate with your doctor, especially with breathing changes or kidney concerns.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.