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Carbon Dioxide (Total) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of carbon dioxide dissolved in your blood plasma, which helps assess how well your body is balancing acidity and alkalinity (acid-base balance).

Quick summary

["Your blood’s carbon dioxide levels play a key role in maintaining healthy pH and respiratory function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
77143-6
Short code
CO2 SerPlBld-sCnc
Synonyms
CO2 SerPlBld-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
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?

Total carbon dioxide (CO₂) in your blood includes bicarbonate (the main form of CO₂ in plasma) and dissolved CO₂. This measurement helps evaluate your body’s ability to regulate acidity and alkalinity, which is critical for normal metabolism and organ function. It also supports assessment of respiratory and metabolic conditions.

Why Might You Need This Test?

Doctors may order this test to diagnose or monitor conditions affecting acid-base balance, such as respiratory disorders (e.g., chronic obstructive pulmonary disease), metabolic disorders (e.g., kidney disease), or severe dehydration. It can also help guide treatment for conditions like ketoacidosis or alkalosis.

How Is the Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The serum portion of your blood is then analyzed to measure the total carbon dioxide content using specialized laboratory techniques.

What Are Common Results?

Results are typically reported as a numerical value (e.g., mmol/L), but exact ranges can vary by lab. Abnormal results may indicate either too much or too little carbon dioxide in your blood, which can signal underlying health concerns.

Reference range

Adult: 22-28 mmol/LN/A

Specimen: serum

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.

Clinical Significance: Why It Matters

Short name

Total CO₂ (Serum)

Frequently asked questions

How does carbon dioxide in my blood relate to my health?
Carbon dioxide levels help your body maintain a balanced pH. Low levels may suggest hyperventilation or respiratory issues, while high levels could indicate metabolic problems or kidney dysfunction. Your doctor will interpret results in the context of your symptoms and overall health.
What does a low total CO₂ level mean?
A low total CO₂ level may point to conditions like respiratory alkalosis (e.g., from anxiety or rapid breathing) or certain metabolic disorders. It’s important to discuss symptoms like dizziness, fatigue, or shortness of breath with your healthcare provider.
What does a high total CO₂ level mean?
A high total CO₂ level may suggest metabolic acidosis (e.g., from kidney problems or diabetic ketoacidosis) or respiratory acidosis (e.g., from chronic lung disease). Your doctor will evaluate this alongside other tests and symptoms to determine the cause.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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