Oxygen Level (SpO2) Interpreter
Interpret SpO2 pulse oximeter readings and understand oxygen saturation levels.
See what your blood oxygen percentage means.
Enter your pulse oximeter SpO2 reading to see what it means.
For educational reference only. Not a substitute for medical advice. Your data stays in your browser. We do not store, collect, or transmit any information you enter.
SpO2 (peripheral oxygen saturation) measures the percentage of hemoglobin in your blood that is carrying oxygen. A pulse oximeter clips to your fingertip and uses light to estimate this value non-invasively.
SpO2 interpretation ranges:
| SpO2 Reading | Interpretation | Notes |
|---|---|---|
| 95-100% | Normal | Healthy range for most people |
| 90-94% | Below normal | May indicate a respiratory issue; consult a doctor |
| 85-89% | Concerning | Medical attention recommended |
| Below 85% | Critical | Seek emergency medical care immediately |
How pulse oximeters work: The device shines red and infrared light through your finger. Oxygenated hemoglobin absorbs more infrared light, while deoxygenated hemoglobin absorbs more red light. The ratio of absorption determines the SpO2 percentage.
Factors that can affect accuracy:
- Poor circulation or cold fingers can give falsely low readings.
- Dark nail polish (especially black, blue, or green) can interfere with the sensor.
- Bright ambient light can cause errors. Shield the sensor from direct sunlight.
- Carbon monoxide poisoning can give falsely high readings because the sensor cannot distinguish carboxyhemoglobin from oxyhemoglobin.
- Skin pigmentation may slightly affect accuracy in some devices.
- Movement or shivering reduces accuracy. Keep your hand still and warm.
Altitude and SpO2: At higher elevations, lower air pressure means less available oxygen. Residents at high altitudes may normally have SpO2 values of 90-95%. At sea level, readings below 95% may warrant medical evaluation.
The relationship between SpO2 and PaO2: SpO2 and PaO2 (partial pressure of oxygen in arterial blood, measured in mmHg) follow the oxygen-hemoglobin dissociation curve, which is not linear:
| SpO2 (%) | Approximate PaO2 (mmHg) |
|---|---|
| 100 | Above 100 |
| 97 | 90-100 |
| 95 | 80 |
| 90 | 60 |
| 85 | 50 |
| 80 | 45 |
| 75 | 40 |
Important disclaimer: This tool is for general educational reference only. It is not a substitute for professional medical advice, diagnosis, or treatment. If you have concerns about your oxygen levels, consult a healthcare provider.