Oxygen Saturation in Blood (Arterial) from Oxygen Pressure (Partial Pressure)
This test measures how well oxygen is being carried in your bloodstream by comparing the oxygen levels in your blood to the surrounding oxygen pressure. It helps assess lung function and blood oxygen efficiency.
["Evaluates oxygen delivery and lung efficiency using a direct relationship between blood oxygen saturation and ambient oxygen pressure."]
Key facts at a glance
- LOINC
- 51733-4
- Short code
- SaO2 % BldA from pO2
- Synonyms
- SaO2 % BldA from pO2
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 80
- Ref high
- 100
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- calculated-from-oxygen-partial-pressure
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your healthcare provider may order this test if you have symptoms like shortness of breath, fatigue, or signs of poor oxygenation, such as blue lips or fingernails. It’s also used in monitoring conditions like lung diseases, heart problems, or during surgeries requiring precise oxygen management.
How the Test Works
A blood sample is taken from an artery (often in your arm) and analyzed to determine the oxygen saturation level relative to the oxygen pressure in your blood. This relationship helps identify how efficiently your body is utilizing oxygen.
What to Expect Before the Test
No special preparation is needed. You may experience a brief pinch or discomfort from the needle, but it’s usually over quickly. If you’re on oxygen therapy, your provider may guide you on how to proceed.
What the Results Mean
Results are expressed as a percentage (e.g., 95%) showing how saturated your blood is with oxygen. Lower values may indicate lung issues, poor circulation, or other health problems that need further evaluation.
Reference range
NCBI: PaO2 80-100 mmHgN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Arterial Oxygen Saturation (SaO₂) from PO₂
Frequently asked questions
What does an abnormal result mean?
Can I eat or drink before this test?
Is there any risk or discomfort associated with this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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 17, 2026. · Read our editorial policy