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Pulse Oximetry (Oxygen Saturation via Finger Probe)

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

This test measures how much oxygen is in your blood using a small sensor placed on your finger. It helps doctors check your breathing and overall health.

Quick summary

["A pulse oximeter provides a quick, non-invasive way to monitor oxygen levels in your blood."]

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

Key facts at a glance

LOINC
59413-5
Short code
SaO2 p Tx % BldA PulseOx
Synonyms
SaO2 p Tx % BldA PulseOx
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
pulse-oximetry
CPT
85610
SNOMED
396252006
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

How It Works

A small sensor attached to your finger shines light through your blood vessels. Your body absorbs different amounts of light depending on whether your blood is oxygen-rich or oxygen-poor. The sensor detects these differences and calculates your oxygen saturation level, usually expressed as a percentage (e.g., 95%).

What It Measures

Oxygen saturation (SpO₂) reflects the percentage of oxygen-bound hemoglobin in your blood. Normal values typically range between 95% and 100%, but this can vary based on health conditions, altitude, or other factors.

Why It’s Done

Doctors use pulse oximetry to assess breathing efficiency, monitor chronic conditions like heart or lung disease, check for low oxygen levels during surgery or anesthesia, or evaluate symptoms such as shortness of breath, fatigue, or dizziness.

Common Uses

This test is often performed at home, in hospitals, or during routine check-ups to ensure your body is getting enough oxygen. It’s also used in emergency settings to quickly identify potential breathing problems.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: whole-blood

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Pulse Ox

Frequently asked questions

What causes false low readings?
False low oxygen saturation readings can occur if your finger is cold, swollen, or poorly perfused (e.g., from poor circulation). Motion, nail polish, or dark skin may also interfere. If your results seem off, your healthcare provider may repeat the test or use additional methods to confirm.
What does a reading below 90% mean?
A reading below 90% is generally considered low and may signal a need for further medical evaluation. This could indicate breathing difficulties, heart problems, or other health concerns. Your doctor will discuss next steps based on your symptoms and overall health.
Can I use this test at home?
Yes, many pulse oximeters are available over the counter for home use. However, if you have chronic health conditions or symptoms like shortness of breath, always consult your healthcare provider before relying solely on home readings. Some devices may not be as accurate as those used in clinical settings.
  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