Total Carbon Dioxide (Plasma or Serum) Calculated from Blood Gas Analysis
This test measures the amount of carbon dioxide in your blood, calculated from a blood gas analysis. It reflects how well your body is balancing acidity and alkalinity.
["Helps assess your body’s acid-base balance and potential respiratory or metabolic issues."]
Key facts at a glance
- LOINC
- 53089-9
- Short code
- CO2 Fld.NB Calc-sCnc
- Synonyms
- CO2 Fld.NB Calc-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 22
- Ref high
- 28
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- calculated
- CPT
- 82374
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
A blood gas analysis includes multiple measurements, and this test calculates the total carbon dioxide (CO₂) present in your blood. CO₂ is a byproduct of metabolism and helps regulate your body’s pH (acidity/alkalinity). The test uses results from oxygen, pH, and bicarbonate levels to derive this value.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms like shortness of breath, rapid breathing, or signs of acid-base imbalance. It’s also used in monitoring conditions like chronic obstructive pulmonary disease (COPD), kidney disease, or metabolic disorders.
How Is This Test Performed?
A small blood sample is taken from a vein in your arm. The blood is analyzed in a lab to measure CO₂ levels indirectly, often alongside other blood gas measurements like pH and bicarbonate.
What Are Common Causes of Abnormal Results?
Low total CO₂ levels may suggest respiratory alkalosis (too much CO₂ is lost) or metabolic alkalosis. High levels could indicate respiratory acidosis (too much CO₂ is retained) or metabolic conditions like kidney disease.
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 is critical for diagnosing and managing conditions affecting acid-base balance, such as lung diseases, kidney disorders, or severe dehydration. It helps doctors adjust treatments like oxygen therapy or medication to restore balance.
Short name
Total CO₂ (calc)
Frequently asked questions
What does a low total CO₂ level mean?
What does a high total CO₂ level mean?
How often should I get 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