Blood
Bicarbonate (CO₂)
Also known as: HCO3
CONVERT & COMPARE
mEq/L
=
26
mmol/L
Reference ranges by source
Published adult intervals: 6, from 4 named sources, shown in mEq/L.
SOURCE
SEX
AGE
RANGE
VISUAL
CITE
U
UK Pathology Harmony
All
≥18y
22 – 29 mEq/L
U
UK Pathology Harmony
All · ≥18y
22 – 29 mEq/L
Ages 0–17 (CALIPER)
14 age- and sex-stratified entries from the Canadian Laboratory Initiative on Pediatric Reference Intervals.
SOURCE
SEX
AGE
RANGE
VISUAL
CITE
About Bicarbonate (CO₂)
A carbon dioxide (CO2) blood test measures the amount of carbon dioxide in your blood. Carbon dioxide is an odorless, colorless gas. It is a waste product from metabolism, the process your body uses to make energy from food you eat.
Most of the carbon dioxide in your body is in the form of bicarbonate (HCO3), which is a type of electrolyte. Electrolytes are electrically charged minerals that help control the amount of fluid and the balance of acids and bases (pH balance) in your body.
Your blood carries carbon dioxide to your lungs, and then you breathe it out. Too much or too little carbon dioxide in your blood can be a sign of a health problem.
Main source: MedlinePlus ↗
Useful for
Often part of a group of tests called an electrolyte panel, which may be part of a routine checkup.
May help diagnose or monitor conditions related to an electrolyte imbalance, including high blood pressure and diseases of the kidneys, lungs, or liver.
Check for side effects of certain medicines that can cause electrolyte imbalances.
Main source: MedlinePlus ↗
Interpretation
Abnormal test results may be a sign that your body is having a hard time keeping the right acid-base balance (pH balance).
Too much CO2 in the blood can be a sign of many conditions, including lung diseases, Cushing's syndrome, kidney failure, and metabolic alkalosis.
Too little CO2 in the blood may be a sign of Addison disease, diabetic ketoacidosis, shock, metabolic acidosis, and respiratory alkalosis.
If your test results are not in the normal range, it doesn't necessarily mean you have a medical condition that needs treatment. Your provider may order other tests to confirm a diagnosis.
For general wellness information only. Talk to a clinician about your specific results.
Main source: MedlinePlus ↗
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Related biomarkers
More tests in the blood category.
Sources
M
Mayo Clinic Laboratories
L
Labcorp
R
RCPA / AACB Australasian Harmonised Reference Intervals
U
UK Pathology Harmony
C
CALIPER: Canadian Pediatric Reference Intervals
Last updated 2026-05-02
This page presents source-specific reference data and sourced explanations. For general wellness information only. This is not medical advice. For diagnosis or treatment of any condition, talk to a qualified clinician.