Total Carbon Dioxide in Blood (as Bicarbonate)
This test measures the amount of carbon dioxide in your blood, primarily in the form of bicarbonate, which helps regulate your body’s acid-base balance.
["Your blood’s CO₂ levels help maintain healthy pH and support normal breathing and metabolism."]
Key facts at a glance
- LOINC
- 2026-3
- Short code
- CO2 BldA-sCnc
- Synonyms
- CO2 BldA-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 22
- Ref high
- 28
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82374
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
Total carbon dioxide in your blood is a key indicator of how well your body is balancing acids and bases. It includes bicarbonate (the main form of CO₂ in blood) and dissolved CO₂ gas. This balance is crucial for preventing conditions like acidosis or alkalosis, which can affect your organs and muscles.
Why Might You Need This Test?
Doctors may order this test to check for respiratory or metabolic disorders, such as chronic obstructive pulmonary disease (COPD), kidney problems, or conditions affecting how your body uses oxygen and carbon dioxide.
How Is the Test Performed?
A small blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure the total carbon dioxide content.
What Are Common Causes of Abnormal Results?
High levels may suggest respiratory alkalosis (too much CO₂ loss) or metabolic alkalosis, while low levels could indicate respiratory acidosis (too much CO₂ retention) or metabolic acidosis.
Reference range
Adult: 22-28 mmol/LN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test helps diagnose and monitor conditions affecting acid-base balance, such as kidney disease, lung disorders, or severe dehydration. It’s also used in intensive care settings to guide treatment for patients with breathing or metabolic issues.
Short name
Total CO₂ (blood)
Frequently asked questions
Could this test be affected by recent exercise or diet?
What do the results mean if they’re outside of normal ranges?
Is this test painful or uncomfortable?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy