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Total Carbon Dioxide (Plasma) by Chemical Equilibrium Method

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

This test measures the amount of carbon dioxide dissolved in your blood plasma, which helps assess your body’s ability to balance acidity and alkalinity.

Quick summary

["This test helps evaluate your blood’s acid-base balance and kidney function."]

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

Key facts at a glance

LOINC
14040-0
Short code
CO2 Stl-sCnc
Synonyms
CO2 Stl-sCnc
Category
chemistry
Sample
stool
Container
Clean 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
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions affecting acid-base balance, such as metabolic acidosis or alkalosis, or to monitor kidney function, especially if you have symptoms like fatigue, confusion, or unusual breathing patterns.

What Does the Test Measure?

The test measures the total amount of carbon dioxide in your blood plasma, which is part of how your body regulates blood pH. It reflects the balance between carbon dioxide and bicarbonate ions, which are key in maintaining normal acid-base chemistry.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate plasma, where the carbon dioxide levels are measured. This test is typically done on fresh plasma to ensure accurate results.

What Are Common Uses?

This test is commonly used in conjunction with other blood gas tests (like pH and bicarbonate levels) to diagnose and manage conditions such as respiratory or metabolic disorders, kidney disease, or fluid and electrolyte imbalances.

Reference range

Adult: 22-28 mmol/LN/A

Specimen: stool

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)

Frequently asked questions

What does a low total CO₂ level mean?
A low total CO₂ level may suggest metabolic alkalosis (too much bicarbonate) or conditions that reduce carbon dioxide production, such as overuse of antacids or certain medications. It can also occur in severe dehydration or kidney issues.
What does a high total CO₂ level mean?
A high total CO₂ level may indicate metabolic acidosis (too little bicarbonate) or conditions that increase carbon dioxide retention, such as chronic obstructive pulmonary disease (COPD) or kidney problems. It can also be seen in diabetic ketoacidosis or severe dehydration.
How often should I get this test?
The frequency depends on your health condition and treatment plan. Your healthcare provider will determine how often this test is needed based on your symptoms, medical history, and any ongoing treatments.
  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