Arterial Blood Gas (ABG)
A blood test from an artery that measures oxygen, carbon dioxide and acid levels in the blood.
Quick Summary
To assess breathing and acid-base balance in serious illness.
pH, oxygen, carbon dioxide, bicarbonate and lactate.
Done in hospital; no preparation.
Overview
Blood is usually taken from the wrist artery, which can be more painful than a vein.
Results guide oxygen and ventilation.
What It Measures
pH
Acid level.
PaO2 and PaCO2
Oxygen and carbon dioxide.
Bicarbonate
Body's buffer.
How It's Performed
- 01
Check
Circulation in the hand is checked.
- 02
Sample
A small needle into the wrist artery.
- 03
Pressure
Firm pressure for several minutes.
Reference Ranges
Note: Normal ranges vary by laboratory. Consult your report for the specific reference used.
| Parameter | Typical Range (Adult) | Units |
|---|---|---|
| pH | 7.35–7.45 | pH units |
| PaO2 | 80–100 | mmHg |
| PaCO2 | 35–45 | mmHg |
Interpreting Results & Next Steps
Discuss with Doctor
Your doctor will explain the report and what happens next.
If values are Low:
Low oxygen or pH needs urgent treatment.
If values are High:
High carbon dioxide suggests breathing failure.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Arterial Blood Gas (ABG) Test(opens in a new tab) · MedlinePlus, US National Library of Medicine