Bicarbonate (CO2)

What is Bicarbonate (CO2)?

Bicarbonate, reported on metabolic panels as total carbon dioxide (CO2), is the body's main buffer against acid and a key indicator of acid-base balance. It is regulated together by the kidneys and lungs.

The bicarbonate (total CO2) value on a blood panel mostly measures bicarbonate, the base that neutralizes acids and keeps blood pH within its narrow healthy window. The kidneys and lungs jointly manage this balance: the lungs adjust how much carbon dioxide is exhaled minute to minute, while the kidneys slowly retain or excrete bicarbonate and acid over days. A low bicarbonate can reflect metabolic acidosis from conditions such as uncontrolled diabetes, kidney disease, or severe diarrhea, whereas a high bicarbonate can reflect metabolic alkalosis from prolonged vomiting or certain diuretics. Because bicarbonate is one half of the acid-base story, it is interpreted with chloride, the anion gap, and, when needed, an arterial blood gas.

Tests often checked alongside this

• Chloride — paired with bicarbonate to read acid-base patterns
• Anion Gap — distinguishes types of metabolic acidosis
• Sodium and potassium — complete the electrolyte panel
• Arterial blood gas — gives a fuller acid-base assessment when needed

How this can show up in how you look and feel

• Low bicarbonate (acidosis) can be associated with rapid breathing, fatigue, and confusion
• High bicarbonate (alkalosis) can be associated with muscle twitching, irritability, and tingling
• Mild changes often produce no symptoms

What can affect this marker

• Kidney function and lung (breathing) status
• Vomiting or diarrhea
• Blood-sugar control in diabetes
• Medications such as some diuretics and excess antacids

What to track over time

• Bicarbonate with chloride and the anion gap
• Breathing changes and energy levels
• Episodes of vomiting or diarrhea
• Management of any diabetes or kidney condition

What to ask your doctor

• Does my bicarbonate suggest acidosis or alkalosis?
• Do I need an anion gap or blood gas to clarify the cause?
• Could a medication or my blood sugar be involved?
• How soon should this be rechecked?

This glossary entry is for informational purposes only and is not a substitute for professional medical advice. Read our Terms of Use.