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Oxygen Saturation in Arterial Blood

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

This test measures how much oxygen is bound to hemoglobin in your blood from an artery, typically drawn from your arm. It’s used to assess lung function and oxygen levels in the blood.

Quick summary

["Checks how well your lungs deliver oxygen to your blood—critical for diagnosing breathing issues or low oxygen levels."]

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

Key facts at a glance

LOINC
8839-3
Short code
SaO2 % AO root
Synonyms
SaO2 % AO root
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

Oxygen saturation (SaO₂) reflects the percentage of hemoglobin molecules carrying oxygen in your arterial blood. Normal values indicate efficient oxygen transport, while lower values may signal lung problems, anemia, or other conditions impairing oxygen delivery.

Why It’s Done

Doctors order this test to evaluate lung health, detect conditions like pneumonia, asthma, or sleep apnea, or monitor patients with chronic respiratory diseases. It’s also used before surgeries or in cases of suspected low oxygen levels.

How It’s Performed

A small sample of blood is taken from an artery in your arm using a needle. A sensor attached to the probe measures oxygen saturation without drawing blood for lab analysis. Results are displayed in real-time.

Common Conditions Monitored

Low SaO₂ levels may indicate breathing difficulties, heart problems, or blood disorders. High values (rare) could suggest polycythemia (excess red blood cells) or other conditions affecting oxygen binding.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

SaO₂ (Arterial Oxygen Saturation)

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within minutes after the procedure, as the sensor provides immediate feedback. Lab confirmation may take additional time if further analysis is needed.
Can I eat or drink before this test?
No special preparation is required. You can eat, drink, or take medications as usual, as this test only involves a quick blood draw from an artery.
Is there any pain or discomfort during the test?
You may feel a slight pinch when the needle is inserted, but the procedure is quick and usually painless. Most people experience minimal discomfort afterward.
  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