Logging blood oxygen (SpO₂) from a pulse oximeter
Blood oxygen saturation (SpO₂) needs a pulse oximeter, which uses two wavelengths of light. A phone camera can't do that, so the app records the value you read from your oximeter.
Get a good oximeter reading
- Sit still and warm your hands.
- Remove nail polish or false nails from that finger.
- Keep your hand still and at heart level for about a minute, until the number steadies.
- Log the value in the app.
Things that affect accuracy
- Cold hands and poor circulation.
- Movement.
- Nail polish.
- Skin pigmentation — the FDA has noted that pulse oximeters can be less accurate in people with darker skin.
When to get help
Many healthy people read 95–100%, but what's normal for you can differ. If your reading is low or you're short of breath, contact a doctor rather than relying on a home reading.
FAQ
- Why can't the camera measure SpO₂?
- Oxygen saturation is worked out by comparing how two specific wavelengths of light are absorbed. A phone camera and flash aren't built for that, so the app never claims to.
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