What is SpO2?
SpO2 stands for peripheral oxygen saturation — the percentage of your hemoglobin that’s carrying oxygen. For most healthy people, a normal SpO2 is about 95–100%. The device also displays your pulse rate in beats per minute.How does a pulse oximeter work?
It shines light through your fingertip and measures how much is absorbed by oxygen-rich versus oxygen-poor blood, calculating a saturation estimate in seconds. Because it reads through the skin, it’s an estimate — accurate enough for trends in most people, but sensitive to a few conditions.What affects accuracy?
- Cold hands or poor circulation can weaken the signal.
- Nail polish and artificial nails (especially dark colors) can interfere — remove them or try another finger.
- Movement during the reading can throw it off.
- Readings can be less reliable at very low oxygen levels and, research has noted, less accurate on darker skin tones in some cases.
How to use the readings well
Watch the trend rather than fixating on a single number, and always weigh the reading against how you feel. A normal number doesn’t override real symptoms, and a borderline number in someone who feels fine may just be a measurement issue — re-check with good technique. People with lung conditions should follow the targets their doctor sets. SonoHealth offers a fingertip Pulse Oximeter for simple home spot-checks of oxygen and pulse — see it at SonoHealth.com.Related: Normal Oxygen Levels · Oximetry With COPD or Asthma · Breathing Relief at Home