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Total Serum Carbon Dioxide (TSC) or Bicarbonate Equivalent (Calculated)

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

This test measures the amount of carbon dioxide in your blood, which helps your body maintain proper acid-base balance. It indirectly reflects bicarbonate levels, a key component in buffering blood acidity.

Quick summary

["Your blood’s carbon dioxide and bicarbonate balance is critical for staying healthy, especially for breathing and kidney function."]

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

Key facts at a glance

LOINC
51781-3
Short code
CO2 BldC Calc-sCnc
Synonyms
CO2 BldC 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

What Does This Test Measure?

Total serum carbon dioxide (TSC) is calculated from your blood’s pH, oxygen, and carbon dioxide pressure. It reflects how well your body is balancing acids and bases, which is vital for normal metabolism and organ function. Unlike direct bicarbonate measurements, TSC provides an estimate based on chemical principles.

Why Is This Test Done?

Doctors may order this test to check for conditions affecting acid-base balance, such as respiratory or metabolic disorders. It can help diagnose or monitor conditions like chronic obstructive pulmonary disease (COPD), kidney disease, or diabetic ketoacidosis.

Common Conditions Monitored

High or low TSC levels may signal issues like hyperventilation (rapid breathing), kidney problems, or fluid imbalances. It’s often used alongside other blood tests (like pH or electrolytes) for a full picture of your blood chemistry.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to calculate carbon dioxide equivalents based on standard chemical methods.

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.

Clinical Significance: Acid-Base Balance and Health Risks

Short name

TSC or Bicarbonate Equivalent

Frequently asked questions

What causes abnormal TSC results?
Abnormal TSC results may indicate underlying conditions like respiratory acidosis (e.g., from lung disease), metabolic alkalosis (e.g., from vomiting or diuretics), or kidney dysfunction. Always discuss symptoms with your doctor, as results can vary based on your overall health.
How often should I get this test?
Frequency depends on your health status. Doctors may recommend regular checks if you have chronic conditions like kidney disease, diabetes, or lung disorders. Follow-up tests are often scheduled based on your treatment plan.
Can diet or lifestyle affect TSC results?
Dietary changes (e.g., high protein or low-carb diets) or extreme physical activity can temporarily alter blood chemistry, including TSC. Avoid heavy meals or caffeine before testing if instructed by your lab.
  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