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Oxygen Saturation in Arterial Blood (SaO₂)

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

This test measures how well oxygen is being carried in your blood from your lungs to the rest of your body.

Quick summary

["Assesses oxygen levels in your blood to check for breathing or circulation issues."]

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

Key facts at a glance

LOINC
8847-6
Short code
SaO2 % RV
Synonyms
SaO2 % RV
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

Your blood carries oxygen from your lungs to every part of your body, including your heart, brain, and muscles. This test helps doctors see if your body is getting enough oxygen. Low levels can signal problems like poor breathing, heart conditions, or other health concerns.

How It’s Done

A small sample of blood is taken from an artery in your arm or wrist. The sample is analyzed quickly in a lab to measure how saturated (filled with oxygen) your red blood cells are.

Common Uses

Doctors may order this test if you have symptoms like shortness of breath, fatigue, or rapid heartbeat. It’s also used before surgeries, during anesthesia, or to monitor conditions like chronic obstructive pulmonary disease (COPD) or heart failure.

What to Expect Before the Test

There’s usually no special preparation needed. You may feel a slight pinch when the blood is drawn, but it’s a quick and common procedure. If you’re on blood thinners, let your doctor know before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Arterial Oxygen Saturation

Frequently asked questions

What does a low or high oxygen saturation level mean?
Low oxygen saturation (below 90%) can indicate breathing problems, such as pneumonia, asthma, or lung disease. Very low levels (below 85%) may require immediate medical attention. High levels (above 95%) are usually normal but can sometimes signal conditions like high altitude or certain blood disorders.
How long does it take to get results?
Results are typically available within minutes to a few hours, depending on your lab’s process. Your doctor will discuss them with you during your visit.
Can I eat or drink before this test?
You can eat and drink normally before this test, as it doesn’t require fasting. However, if you’re scheduled for a procedure that requires fasting, follow your doctor’s instructions.
  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