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Oxygen Saturation in Arterial Blood (via Pulse Oximetry Probe)

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

This test measures how well oxygen is being carried in your blood using a small sensor placed on your finger, ear, or toe. It’s often used to check oxygen levels quickly during routine visits or in emergency situations.

Quick summary

["A simple, non-invasive way to monitor oxygen efficiency in your bloodstream."]

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

Key facts at a glance

LOINC
8853-4
Short code
SaO2 % PA-R
Synonyms
SaO2 % PA-R
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

How This Test Works

A small sensor attached to your body (like a clip or probe) sends light through your skin to measure the amount of oxygen bound to hemoglobin in your blood. The device calculates the percentage of oxygen-saturated hemoglobin, which is displayed as a number (e.g., 95%).

Why It’s Done

Doctors may order this test to monitor oxygen levels in people with conditions like heart disease, lung problems (e.g., asthma, COPD), or those recovering from surgery. It’s also used during anesthesia, in the ICU, or for patients with symptoms like shortness of breath or fatigue.

What to Expect

You’ll likely feel a slight pressure or warmth from the sensor, but no pain. The test takes just a few minutes. If you have a finger probe, you may need to keep your hand still while the sensor reads your blood flow.

Preparation

No special preparation is needed. Avoid removing the sensor unless instructed by your healthcare provider. If you’re using a finger probe, avoid applying lotion or perfumes to your fingertip before testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low oxygen saturation (below 90%) may indicate problems like poor lung function, heart issues, or conditions like anemia or sleep apnea. High saturation (above 100%) is rare but can occur in rare cases of polycythemia (overproduction of red blood cells). Always discuss results with your doctor, as they’ll consider your overall health and symptoms.

Short name

O₂ Saturation (Pulse Oximetry)

Frequently asked questions

What causes false low readings?
False low readings can occur if the sensor is dirty, improperly placed, or if you’re moving too much. Cold hands or hands with poor circulation may also affect accuracy. If you suspect an error, ask your provider to retest or use a different sensor location.
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 weekly, monthly, or only as needed (e.g., during an illness). Regular monitoring helps track changes in your oxygen levels over time.
Can I eat or drink before this test?
No special diet or fasting is required for this test. You can eat, drink, or take medications as usual. However, if you’re using a finger probe, avoid applying lotion or perfumes to your fingertip before testing to prevent interference.
  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