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Total Carbon Dioxide in Blood (Calculated from Serum Chloride and pH)

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

This test measures the total amount of carbon dioxide in your blood, calculated from other blood measurements. It helps assess how well your body is balancing acidity and alkalinity.

Quick summary

["This test helps evaluate your blood’s acid-base balance and potential metabolic issues."]

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

Key facts at a glance

LOINC
57923-5
Short code
CO2 BldCoV Calc-sCnc
Synonyms
CO2 BldCoV Calc-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
Method
calculated
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

Why Is This Test Done?

Your doctor may order this test to check for conditions like metabolic acidosis or alkalosis, kidney function, or respiratory problems. It’s often used alongside other blood tests to diagnose or monitor conditions affecting how your body regulates acids and bases.

What Does the Result Mean?

Results are not provided as a single numeric range since they’re calculated from pH and chloride levels. Abnormal values may suggest imbalances that require further medical evaluation.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The serum is analyzed to calculate total CO₂ levels based on pH and chloride concentration.

Common Conditions Monitored

This test is useful for monitoring conditions like kidney disease, respiratory disorders, or metabolic disorders that affect acid-base balance.

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 (Calc)

Frequently asked questions

What does a high or low total CO₂ level mean?
A high or low calculated total CO₂ level may signal an imbalance in your body’s acid-base chemistry. Your doctor will interpret results in the context of your overall health and other test findings to determine if further action is needed.
Can I eat or drink anything before this test?
For this test, you may need to fast or avoid certain foods/drinks for a specified period, depending on your doctor’s instructions. Follow your healthcare provider’s guidance to ensure accurate results.
How long will it take to get my results?
Results are typically available within a few days, depending on lab processing times. Your doctor will discuss the findings with you during your follow-up visit.
  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