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Total Carbon Dioxide in Blood (Plasma/Serum) Concentration

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

This test measures the amount of carbon dioxide dissolved in your blood plasma or serum, which helps assess how well your body is balancing acidity and alkalinity.

Quick summary

["Your blood’s CO₂ levels help determine if your body is properly regulating acid-base balance, often linked to breathing or kidney function."]

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

Key facts at a glance

LOINC
97545-8
Short code
CO2 BldCV-sCnc
Synonyms
CO2 BldCV-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 CO₂ reflects the combined form of carbon dioxide in your blood, including bicarbonate (the most abundant form) and dissolved CO₂ gas. This measurement is critical for evaluating how efficiently your lungs and kidneys maintain normal blood pH.

Why Might You Need This Test?

Doctors may order this test if you have symptoms like shortness of breath, fatigue, or signs of metabolic or respiratory disorders. It’s also used in monitoring conditions like chronic obstructive pulmonary disease (COPD), kidney disease, or acid-base imbalances.

How Is This Test Performed?

A small blood sample is drawn from a vein, typically in your arm. The sample is then processed to measure the total CO₂ concentration in plasma or serum using specialized laboratory techniques.

What Are Common Reasons for Abnormal Results?

Low levels of total CO₂ may indicate respiratory alkalosis (e.g., hyperventilation) or kidney issues, while high levels could suggest respiratory acidosis (e.g., hypoventilation) or metabolic alkalosis.

Reference range

Adult: 22-28 mmol/LN/A

Specimen: whole-blood

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.

◆Associated findings1

Short name

Total CO₂ (Plasma/Serum)

Frequently asked questions

Could diet or medications affect this test result?
Dietary changes, such as high-protein or high-carbohydrate meals, may temporarily influence blood chemistry, including CO₂ levels. Certain medications, like diuretics or asthma inhalers, could also affect results. Always inform your healthcare provider about all medications or recent dietary changes.
How soon will I get my results, and what do they mean?
Results are typically available within 1–3 business days. Your doctor will interpret them in the context of your symptoms, medical history, and other tests. If your results are abnormal, further evaluation may be needed to determine the cause.
Is this test painful, and what should I expect during the procedure?
The blood draw is mild discomfort for a few seconds, but most people tolerate it well. You may feel a slight pinch when the needle is inserted. Afterward, a bandage is applied, and you can resume normal activities unless your doctor advises otherwise.
  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