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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 arterial blood sample, often used to assess lung function and oxygen delivery to tissues.

Quick summary

["Helps doctors check if your lungs are working properly and if you’re getting enough oxygen."]

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

Key facts at a glance

LOINC
8840-1
Short code
SaO2 % LA
Synonyms
SaO2 % LA
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 Does This Test Measure?

The test evaluates the percentage of oxygen molecules attached to hemoglobin in your red blood cells. This is critical for determining how well your blood is carrying oxygen to your body’s tissues. Normal values can vary slightly based on altitude, health status, and other factors, so results are interpreted by a healthcare provider.

Why Might You Need This Test?

Doctors order this test when they suspect conditions like respiratory issues (e.g., asthma, pneumonia), heart problems, or low oxygen levels. It’s also used during surgeries, in intensive care units, or before procedures that could affect breathing.

Preparation for the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw if it’s part of a larger test panel. You’ll typically have a small needle inserted into an arm vein to collect a small amount of blood.

What to Expect During the Test

The blood draw takes just a few minutes. You may feel a slight pinch or discomfort, but it’s usually over quickly. Afterward, you can resume normal activities, though you might experience mild bruising or soreness at the site.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

SaO₂

Frequently asked questions

What causes low oxygen saturation?
Low oxygen saturation can result from conditions like chronic obstructive pulmonary disease (COPD), pneumonia, anemia, or heart failure. It may also occur during sleep apnea, high altitudes, or if you smoke.
What does a high oxygen saturation mean?
High oxygen saturation might suggest polycythemia (too many red blood cells), overuse of oxygen therapy, or other conditions that increase red blood cell production. It’s not always a cause for concern but should be evaluated by a healthcare provider.
Can I eat or drink before this test?
No specific dietary restrictions apply, but if your blood test includes other components (like glucose or lipids), follow any fasting instructions provided by your doctor.
  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