How accurate is a pulse oximeter?
Last updated September 3, 2026.
A good trend tool, not a precise instrument. The FDA is explicit: real readings can run a few points off true oxygen saturation, with error sources including poor circulation, cold fingers, nail polish, movement, and darker skin pigmentation - the subject of an FDA safety communication. Sit still, warm your hands, remove polish, and watch the direction over time. And symptoms beat the device: serious breathlessness needs urgent care whatever the number says.
What to do
- Control the variables. Warm, still hands and no nail polish clean up most home-reading noise.
- Track the trend. A falling pattern over hours matters more than any one reading.
- Never let a number overrule symptoms. Severe shortness of breath, blue lips, or confusion is an emergency regardless.
- Know your baseline. Your normal reading is the reference point for what "low" means for you.
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