Oxygen Saturation Monitoring via Mixed Venous Blood (O₂ Saturation)
This test measures how well your blood is carrying oxygen from your lungs to the rest of your body. It’s often used in critical care settings to assess lung function and oxygen delivery efficiency.
["Helps doctors check if your body is getting enough oxygen during serious conditions like heart or lung problems."]
Key facts at a glance
- LOINC
- 56875-8
- Short code
- Mixed venous O2 sat monitoring
- Synonyms
- Mixed venous O2 sat monitoring
- 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?
Your blood carries oxygen from the lungs to tissues throughout your body. This test looks at the oxygen saturation level in mixed venous blood—blood that has already circulated through your heart and lungs once. A lower-than-expected saturation may signal issues like poor lung function, heart failure, or blood flow problems.
Why Might You Need This Test?
Doctors may order this test if you’re in the hospital with severe breathing difficulties, heart issues, or after surgery. It helps monitor how well your body is handling oxygen during critical care.
How Is the Test Performed?
A small sample of blood is taken from a vein in your arm or another accessible vein. The blood is analyzed in a lab to measure oxygen saturation levels. This test is often done continuously in intensive care units using specialized equipment.
What Are Common Uses?
This test is primarily used in intensive care settings to track oxygen levels in patients with respiratory or cardiac conditions. It helps guide treatment decisions, such as adjusting oxygen therapy or assessing the effectiveness of medications.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Oxygen saturation monitoring is critical for identifying and managing conditions like acute respiratory distress syndrome (ARDS), heart failure, or severe infections that impair oxygen delivery. Low saturation levels can prompt immediate medical intervention to improve oxygenation.
Short name
Venous O₂ Saturation
Frequently asked questions
What does a mixed venous blood sample mean for me?
How often will I need this test?
Can I eat or drink before 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 16, 2026. · Read our editorial policy