Pulse Oximeter Readings Chart
A pulse oximeter estimates peripheral oxygen saturation (SpO2). The FDA says most healthy people have readings of 95–100%, but a reading is an estimate with uncertainty and must be interpreted with symptoms, trends, altitude, baseline disease and device limitations. The bands below are a general context guide, not a treatment protocol.
Reference Data
| SpO2 Level | Clinical Interpretation | Action Required |
|---|---|---|
| 100% | Normal — fully saturated | None; optimal oxygenation |
| 99% | Normal | None |
| 98% | Normal | None |
| 97% | Normal | None |
| 96% | Normal | None |
| 95% | Normal — lower limit of normal for most adults | None for healthy adults; may warrant monitoring in patients with lung disease |
| 94% | Borderline — may indicate mild hypoxemia | Recheck reading; consider medical evaluation if persistent |
| 93% | Below normal — mild hypoxemia | Seek medical evaluation; may require supplemental oxygen |
| 92% | Mild hypoxemia | Recheck carefully and contact a healthcare provider, especially if persistent or symptomatic |
| 91% | Mild hypoxemia | Prompt medical assessment; do not start or change oxygen without clinical guidance |
| 90% | Hypoxemia threshold — corresponds to PaO2 ~60 mmHg | Seek urgent medical advice; symptoms and the person's prescribed target determine emergency response |
| 85–89% | Moderate hypoxemia | Seek urgent medical assessment; call emergency services if severe or worsening symptoms are present |
| 80–84% | Severe hypoxemia | Emergency medical care; risk of organ dysfunction |
| 75–79% | Critical hypoxemia — visible cyanosis likely | Call emergency services; do not use the displayed number to select a treatment |
| <70% | Life-threatening hypoxemia | Call emergency services; readings this low may also be outside the device's validated range |
Source: FDA Pulse Oximeter Basics: https://www.fda.gov/consumers/consumer-updates/pulse-oximeter-basics ; FDA 510(k) pulse oximeter guidance: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/pulse-oximeters-premarket-notification-submissions-510ks-guidance-industry-and-food-drug-administration-staff
How to Interpret This Data
Pulse oximetry works by passing two wavelengths of light (red at 660 nm and infrared at 940 nm) through tissue and measuring the ratio of absorbed light. Oxyhemoglobin and deoxyhemoglobin absorb these wavelengths differently, allowing the device to calculate oxygen saturation. The reading (SpO2) is an estimate of arterial oxygen saturation (SaO2) and is typically accurate to within 2–3% at levels above 80%.
The oxyhemoglobin dissociation curve is sigmoidal, meaning that SpO2 remains relatively stable (above 95%) across a wide range of PaO2 values, but drops rapidly once PaO2 falls below approximately 60 mmHg (corresponding to SpO2 ~90%). This is why 90% is considered a critical threshold — small further decreases in PaO2 cause disproportionately large drops in saturation. At SpO2 below 80%, pulse oximeter accuracy degrades significantly as most devices are calibrated using data from healthy volunteers desaturated only to 75–80%.
Several factors can produce inaccurate pulse oximeter readings: poor perfusion (cold fingers, hypotension), nail polish (especially dark colors), skin pigmentation (FDA has acknowledged reduced accuracy in individuals with darker skin tones), carboxyhemoglobin (carbon monoxide poisoning falsely elevates SpO2), methemoglobinemia, excessive motion artifact, and ambient light interference. Always correlate SpO2 readings with clinical assessment and obtain arterial blood gas analysis for definitive oxygenation measurement in critically ill patients.
Frequently Asked Questions
What is a normal pulse oximeter reading?
A normal pulse oximeter reading (SpO2) for a healthy adult at sea level is 95–100%. Readings of 94% or below may indicate hypoxemia and should be evaluated by a healthcare provider, especially if persistent. At high altitudes (above 2,500 m / 8,000 ft), SpO2 of 90–95% may be normal due to lower atmospheric oxygen pressure.
When should I go to the ER based on my pulse oximeter reading?
Seek emergency care if your SpO2 is consistently below 90% or if it drops below 92% and you are experiencing shortness of breath, chest pain, confusion, or bluish discoloration of lips or fingertips. For patients with known chronic lung disease (e.g., COPD), your physician may have set a different threshold — follow their guidance. A single low reading should be rechecked before taking action, as motion artifact is common.
Can a pulse oximeter give a false reading?
Yes. Poor circulation, skin pigmentation, skin thickness or temperature, tobacco use, nail polish, movement and ambient light can affect readings. The FDA recognizes accuracy differences associated with skin pigmentation but does not support applying a single correction factor to an individual's reading.