Blood and lab tests
What Does Bicarbonate (CO2) Mean on a Blood Test?
Bicarbonate · say it: by-KAR-buh-nateAlso written: HCO3, CO2, total CO2, TCO2, bicarb
Short answer
Bicarbonate is an electrolyte that helps keep your blood from becoming too acidic. It is often listed as CO2 on lab reports.
What it means
Bicarbonate is a chemical in the blood that acts as a buffer. It soaks up extra acid and helps hold the blood's acid level within a narrow zone. The kidneys and lungs work together to control it: the kidneys keep or release bicarbonate, and the lungs breathe out carbon dioxide.
Bicarbonate is part of the basic and comprehensive metabolic panels and of electrolyte tests. US reports often call it "CO2" or "total CO2", because most of the carbon dioxide in blood is carried as bicarbonate. A low value can suggest the blood holds too much acid, which happens with kidney problems, severe diarrhea or diabetic ketoacidosis. A high value can come from repeated vomiting, some water pills (diuretics) or long-standing lung disease.
The "CO2" on a metabolic panel is not the same as the pCO2 on an arterial blood gas. pCO2 measures carbon dioxide gas pressure and mainly reflects breathing, while bicarbonate on a panel is mainly a kidney and metabolic measure.
Where you may see it
- Basic and comprehensive metabolic panels, labeled "CO2" or "Bicarbonate"
- Arterial or venous blood gas reports, listed as "HCO3"
- Kidney clinic blood results
📄 How it looks on a report
CO2 19 mmol/L L
🙅 What it does not mean
- CO2 on your blood test does not mean you are breathing out too little or too much. On a metabolic panel it mostly measures bicarbonate.
- A low bicarbonate does not reveal the cause by itself. Doctors combine it with the anion gap, chloride and your history.
- This result is not about baking soda in your diet. The body controls bicarbonate tightly, and the number reflects that control.
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Bicarbonate”
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💊 Medicines whose labels mention “Bicarbonate”
Plain-English explanations of each medicine, from its official FDA label.
- Furosemide
A loop diuretic, a type of medicine that helps the body get rid of extra fluid through urine
- Tetracycline
an antibiotic of the tetracycline type
🔗 Read more from trusted sources
- “Bicarbonate” on MedlinePlus ↗
US National Library of Medicine
- MedlinePlus lab test guides ↗
US National Library of Medicine
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