CO2

Acid–BaseMetabolism & EnergyBlood

Total CO2 on a blood chemistry panel mainly reflects bicarbonate — the body's primary chemical buffer that keeps blood pH within a tight range. Bicarbonate levels are managed by the kidneys and shift in response to breathing patterns.

Why it matters: Higher or lower CO2 (bicarbonate) values can indicate the body is compensating for acid-base shifts, whether from breathing rate changes, kidney filtering changes, or metabolic states like prolonged vomiting or kidney conditions.

Reference Range
23.0 – 29.0mEq/L
23
29LowNormalHigh
What Moves It

May increase with:

Hyperventilation
Metabolic alkalosis

May decrease with:

Hypoventilation
Metabolic acidosis
Associated Conditions
Respiratory failureMetabolic acidosisMetabolic alkalosis
Related Markers
BicarbonatepH
Common questions

What is CO2?

Total CO2 on a blood chemistry panel mainly reflects bicarbonate — the body's primary chemical buffer that keeps blood pH within a tight range. Bicarbonate levels are managed by the kidneys and shift in response to breathing patterns.

What might a high or low CO2 mean?

Higher or lower CO2 (bicarbonate) values can indicate the body is compensating for acid-base shifts, whether from breathing rate changes, kidney filtering changes, or metabolic states like prolonged vomiting or kidney conditions.

What is the typical reference range for CO2?

The general-population reference range shown here is 23 – 29 mEq/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.

What can affect CO2?

It may be higher with: Hyperventilation, Metabolic alkalosis. It may be lower with: Hypoventilation, Metabolic acidosis.

More in Acid–Base
Anion Gap

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