A pulse oximeter is a small, electronic device used to measure blood oxygen saturation and pulse rate non-invasively. It is commonly used in both clinical and at-home settings to monitor how efficiently oxygen is being carried to the parts of your body furthest from your heart. The device works by shining light through a fingertip to determine the amount of oxygen in the blood.
Interpreting Pulse Oximeter Numbers
A pulse oximeter provides two primary measurements: oxygen saturation, displayed as SpO2, and pulse rate. Oxygen saturation represents the percentage of your blood that is carrying oxygen, with a typical reading for a healthy adult at rest falling between 95% and 100%. A level below this may indicate that the heart or lungs are not functioning as they should.
Your pulse rate, the second number displayed, is the number of times your heart beats per minute. For most healthy adults at rest, a normal pulse rate is between 60 and 100 beats per minute. Individuals with certain chronic health conditions, such as chronic obstructive pulmonary disease (COPD), might have a different baseline “normal” SpO2 range, which is determined and monitored by a healthcare provider.
Pulse Oximeter Readings Chart
The numbers provide a quick snapshot of how well your body is distributing oxygen, which is helpful for managing certain health conditions from home or recognizing a potential issue.
| SpO2 Level | Interpretation |
| :— | :— |
| 95% – 100% | Normal |
| 91% – 94% | Low – May warrant monitoring or contacting a doctor. |
| Below 91% | Very Low – This could indicate a significant issue and you should seek medical advice. |
Factors That Affect Accuracy
Several factors can interfere with the accuracy of a pulse oximeter reading, leading to results that are not correct. It is useful to be aware of these variables to ensure the numbers you see are as reliable as possible. Taking steps to mitigate these factors can improve the quality of your measurements.
Movement, such as shivering or shaking, during a reading can cause incorrect numbers. To get a reliable measurement, remain still while the device is in use. The temperature of your skin can also have an impact; if your hands are cold, warming them up before taking a reading is recommended.
Other common issues include the presence of dark nail polish or artificial nails, which can block the light sensor. For an accurate reading, it is best to use a finger that is free of any polish or artificial nail. Poor circulation or improper placement of the device on the finger can also lead to inaccurate data.
When to Contact a Doctor
A single low reading on a pulse oximeter is not always a cause for alarm. The first step should be to re-check the reading after addressing the common accuracy issues, such as warming your hands or removing nail polish. Wait a few minutes and try again to see if the reading stabilizes in the normal range.
If you have persistent low readings, especially if they fall below 91%, it is advisable to contact a healthcare provider. You should seek immediate medical attention if a low oxygen level is accompanied by symptoms such as shortness of breath, chest pain, confusion, difficulty breathing, or a bluish color in the face or lips. A pulse oximeter is a monitoring tool and cannot replace a diagnosis from a medical professional.