Total Carbon Dioxide (Plasma/Serum) – Blood Gas Analysis
This test measures the amount of carbon dioxide in your blood, which helps assess how well your body is balancing acidity and alkalinity (acid-base balance).
["Your blood’s CO₂ levels help doctors check if your lungs are working properly and if your body is maintaining healthy pH levels."]
Key facts at a glance
- LOINC
- 35685-7
- Short code
- CO2 ?Tm Ur-sCnc
- Synonyms
- CO2 ?Tm Ur-sCnc
- Category
- chemistry
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 22
- Ref high
- 28
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82374
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
Total carbon dioxide (CO₂) in your blood includes bicarbonate (the main form of CO₂ in plasma) and dissolved CO₂. This test is often performed alongside other blood gas tests, such as pH and oxygen levels, to evaluate respiratory and metabolic functions.
Why Might You Need This Test?
Doctors may order this test if you have symptoms like shortness of breath, chest pain, confusion, or signs of acid-base imbalances. It’s also used in monitoring conditions like chronic obstructive pulmonary disease (COPD), kidney disease, or metabolic disorders.
How Is the Test Done?
A small blood sample is taken from a vein, usually in your arm. The blood is analyzed immediately or sent to a lab to measure CO₂ levels, often as part of a broader blood gas panel.
What Are Common Results?
Results are typically reported alongside other blood gas values (e.g., pH, oxygen, and bicarbonate) to interpret acid-base status. Abnormal levels may indicate respiratory or metabolic issues.
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.
Total CO₂ levels help diagnose and manage conditions affecting acid-base balance, such as respiratory acidosis (e.g., from lung disease) or metabolic alkalosis (e.g., from vomiting or diuretics). It’s also critical in emergency settings, like severe asthma or heart failure, where CO₂ retention or loss can occur.
Short name
Total CO₂ (Plasma/Serum)
Frequently asked questions
What does a high or low total CO₂ level mean?
How long does it take to get results?
Can I eat or drink before this test?
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