Normal blood oxygen levels
| SpO2 | Meaning |
|---|---|
| 95 to 100% | Normal for healthy people |
| 92 to 94% | Slightly low, recheck and watch for symptoms |
| Below 92% | Low, seek medical advice |
| 88 to 92% | Target range for some people with COPD, set by a doctor |
At high altitude the normal level is lower because there is less oxygen in the air.
How accurate are watches?
Watches and finger clips use light through the skin. Cold hands, movement, nail polish, tattoos and darker skin tones can all change the reading. Medical grade pulse oximeters have been shown to overestimate oxygen in people with darker skin. Use a watch for trends, not for a diagnosis.
For better readings, sit still, keep your hand at heart level, warm your fingers and wait about 30 seconds.
Blood oxygen and sleep
Repeated overnight dips can be a sign of sleep apnoea, a condition where breathing stops and starts. Loud snoring, gasping at night and daytime sleepiness are other signs. If your watch shows frequent dips below 90 percent at night, talk to a doctor. See also the best sleep habits.