Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, specimen conditions and related tests.

Which reference range should I use?

Start with the performing laboratory's own reference interval; clinical cutoffs, when relevant, are separate sourced thresholds used for a specific purpose.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

Bicarbonate (CO2): What Does This Test Measure?

Measures total carbon dioxide in blood, which largely reflects bicarbonate and provides information about acid-base balance.

Test summary

Test name: Bicarbonate (CO2)
Abbreviations: HCO3, HCO3-, CO2, TCO2
Category: Electrolytes / Acid-Base
Panel: Electrolyte Panel / Basic Metabolic Panel
Specimen: Serum / plasma
Common units: mEq/L, mmol/L

What does the test measure?

Measures total carbon dioxide in blood, which largely reflects bicarbonate and provides information about acid-base balance.

Why is the test ordered?

Used with chloride, sodium, potassium and kidney-function tests to assess metabolic acid-base disorders.

Information about a low result

Low bicarbonate/CO2 can occur with metabolic acidosis, selected kidney or gastrointestinal losses, or respiratory compensation.

Information about a high result

High bicarbonate/CO2 can occur with metabolic alkalosis or compensation in some chronic respiratory conditions.

Reference and clinical context

Start with the performing laboratory's reference interval, unit and specimen conditions. Numeric information on this page is stored as sourced example intervals or clinical thresholds.

Reference range 1

>= 23 – <= 29 mmol/L

Population: Adults
Age range: 18
Specimen: Serum / plasma

Example adult Bicarbonate (CO2) reference interval

The source presents these values as a common example reference interval. Laboratory method, age and clinical context can change the range; the user's own report takes priority.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Serum total CO2 largely reflects bicarbonate but is not identical to blood-gas bicarbonate measurement. Acid-base interpretation needs the other electrolytes and clinical context.

Related specialties

Internal Medicine
Nephrology
Emergency Medicine
Pulmonology

Frequently asked questions

More information about this test

Sources

Comprehensive Metabolic Panel — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Example adult intervals for ALT, AST, ALP, albumin, bilirubin, total protein, BUN, creatinine and electrolytes · Verified: Aug 12, 2026
Creatinine Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Creatinine limitations and use with eGFR, BUN and urine testing · Verified: Aug 12, 2026
Electrolyte Panel — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Sodium, potassium, chloride and bicarbonate as an electrolyte panel · Verified: Aug 12, 2026
Chloride Blood Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Chloride interpretation with sodium and acid-base balance · Verified: Aug 12, 2026
Carbon Dioxide (CO2) in Blood — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Serum total CO2/bicarbonate and acid-base context · Verified: Aug 12, 2026