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Oxygen Saturation in Arterial Blood (SaO₂)

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

This test measures how much oxygen is bound to hemoglobin in your blood from an artery (a blood vessel carrying oxygen-rich blood from the heart). It’s commonly used to assess lung function and oxygen levels in the bloodstream.

Quick summary

["A simple test to check if your lungs are delivering enough oxygen to your body."]

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

Key facts at a glance

LOINC
8841-9
Short code
SaO2 % RA
Synonyms
SaO2 % RA
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

Why This Test Matters

Measuring arterial oxygen saturation helps doctors identify issues like poor lung function, breathing problems, or conditions that affect how well your body uses oxygen, such as heart disease or respiratory infections.

How the Test Works

A small sample of blood is taken from an artery (often in your wrist) and analyzed using a device called a pulse oximeter or a blood gas analyzer. The test measures the percentage of oxygen-bound hemoglobin in your blood.

What to Expect Before the Test

You may feel a slight pinch when the blood is drawn, but it’s usually quick and not painful. If you’re anxious, let your healthcare provider know—they can help with comfort measures.

What the Results Mean

Results are typically reported as a percentage (e.g., 95%). A lower percentage may indicate problems with oxygen delivery, while a higher percentage (above 100%) can sometimes be seen in certain medical conditions or with certain devices.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Arterial oxygen saturation is critical for diagnosing conditions like chronic obstructive pulmonary disease (COPD), pneumonia, heart failure, or severe anemia. It also guides treatment decisions for patients with breathing difficulties or those undergoing surgery.

Short name

Arterial Oxygen Saturation

Frequently asked questions

What causes abnormal oxygen saturation levels?
Abnormally low oxygen saturation can be caused by lung diseases (e.g., asthma, COPD), heart problems, high altitude, or conditions that reduce oxygen absorption (e.g., anemia). High levels may occur in rare cases of over-oxygenation or with certain medical devices.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition. Some people may need it regularly if they have chronic lung or heart issues, while others may only need it during specific situations like illness or before surgery.
Can I prepare for this test?
No special preparation is needed. However, if you’re on oxygen therapy, let your healthcare provider know before the test to ensure accurate results.
  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