Sometimes, you won't see a sleep breakdown from your Fitbit device. This is because Fitbit sends one of two types of sleep data:
Staged : Data is returned with 30-second granularity. 'Sleep Stages' levels include deep, light, rem, and wake.
Classic : Data is returned with 60-second granularity. 'Sleep Pattern' levels include asleep, restless, and awake.
According to Fitbit, your Fitbit won't record staged sleep data under the following conditions:
- If you slept in a position that prevented your device from getting a consistent heart-rate reading or wore it too loosely.
- For best results, wear your device higher on your wrist (about 2-3 finger widths above your wrist bone). The band should feel secure but not too tight.
- If you used the Begin Sleep Now option in the Fitbit app (instead of simply wearing your device to bed). For more information on automatic sleep tracking, see Fitbit's FAQ How do I track my sleep with my Fitbit device?
- If you slept for less than 3 hours.
- If your device’s battery is critically low.