Is my CO2 (Bicarbonate) normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal CO2 level?
CO2 on a blood test actually measures bicarbonate — the body's primary acid-base buffer system that maintains blood pH between 7.35-7.45. Normal range is 23-29 mEq/L. Low CO2 can indicate metabolic acidosis (from kidney disease, diabetic ketoacidosis, or severe dehydration). High CO2 can indicate metabolic alkalosis (from excessive vomiting, diuretic use, or respiratory compensation). Bicarbonate is directly linked to kidney function and respiration, making it a critical diagnostic marker for acid-base disorders.
| Range | Values |
|---|---|
| Standard Reference | 23–29 mEq/L |
| High Risk | > 32 mEq/L |
| Low Risk | < 20 mEq/L |
What causes abnormal CO2 levels?
Low bicarbonate (metabolic acidosis): diabetic ketoacidosis, lactic acidosis, renal tubular acidosis, chronic kidney disease (stage 3+), severe diarrhea, and toxic ingestions. High bicarbonate (metabolic alkalosis): prolonged vomiting, diuretic use, primary aldosteronism, milk-alkali syndrome, and chronic respiratory acidosis (COPD — compensatory bicarbonate retention).
When should you see a doctor?
See your doctor if CO2/bicarbonate is below 20 mEq/L or above 32 mEq/L. Severely low bicarbonate (below 15 mEq/L) may indicate a medical emergency (DKA, lactic acidosis, toxic ingestion) requiring urgent treatment. Also consult if bicarbonate is trending downward over serial measurements — this may indicate progressive kidney disease.
CO2 and longevity
Acid-base homeostasis is fundamental to cellular function and enzyme activity. Chronic metabolic acidosis — even mild (bicarbonate 20-22 mEq/L) — is common in chronic kidney disease and accelerates muscle wasting, bone loss, and kidney function decline. Oral sodium bicarbonate supplementation in CKD patients has been shown to slow kidney disease progression and reduce muscle catabolism. The Western diet produces a net acid load that the kidneys must buffer; increasing fruit and vegetable intake (alkaline-forming foods) reduces this burden.
Where to get a CO2 test
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Related biomarkers
These biomarkers are often tested alongside CO2 for a more complete picture.
Frequently asked questions
What is a normal CO2/bicarbonate level?
What causes low bicarbonate?
What is the difference between CO2 and bicarbonate?
What does CO2 mean on a blood test?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.