Symptoms
- Sleep times or stages don't match when you actually fell asleep or woke up
- No sleep data recorded at all for a night
- Watch shows you awake when you were asleep or vice versa
- Sleep score seems inconsistent night to night
Likely causes
- CommonBand worn too loose overnightA loose fit reduces the accuracy of the heart-rate and motion data sleep tracking relies on.
- CommonWatch battery too low to track through the nightIf the watch dies partway through sleep, tracking stops.
- PossibleReading or watching TV in bed before sleep confuses stillness detectionSleep algorithms use stillness and heart rate to guess when sleep starts.
- PossibleSleep mode or Do Not Disturb not setSome watches need sleep mode manually enabled to track properly.
- PossibleInherent limits of wrist-based sleep stagingConsumer wearables estimate sleep stages and are not clinically precise.
What to do
- Charge the watch during the day so it has a full charge overnight, or note its exact overnight window before it dies.
- Wear the band snugger than daytime wear, since a looser overnight fit reduces accuracy.
- Enable sleep mode or bedtime mode if the watch has one.
- Try to stay still and put devices down at the exact time you intend to sleep so the algorithm has clean data.
- Sync the watch each morning and compare a few nights to see if the pattern is consistently off rather than a one-time glitch.
- Update the watch's firmware and companion app for algorithm improvements.
When to call a pro
If you have ongoing sleep concerns beyond tracker accuracy, such as suspected sleep apnea, talk to a doctor rather than relying on consumer wearable data.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.