# How your data reaches VT, and why you sometimes have to sync first

Three paths: the maker’s service, your phone’s health store, or Bluetooth from a VT device. On the health-store path, open the maker’s app first.

Type: practice · Domain: Activities & Lifestyle · Accuracy: Self-reported · Importance: Core

Also called: sync, syncing, Apple Health, Health Connect, Samsung Health, missing data, data not showing, connect my device, which devices work, Oura, Withings, Fitbit, Polar, LibreLinkUp, Nightscout, Bluetooth, switching devices

## Do this

- Connect each device by the most direct route VT offers it: a direct connection to the maker's service where there is one (Oura, Withings, Fitbit, Polar; LibreLinkUp for a FreeStyle Libre; Nightscout for an Ottai; the maker's service for a Sibionics sensor), your phone's health store (Apple Health, Health Connect or Samsung Health) for everything else, and Bluetooth for a VT device.
- On the health-store route, open the maker's app and let it sync before you open VT.
- If a reading is missing in VT, look in the health store first.
- Choose one device for your nights and stay with it.
- During setup, read what each device writes, and know that VT cannot show what a maker withholds.

## Three paths

A direct connection runs through the maker's service: the device syncs to its app, the app to the maker's service, and VT fetches from there when you open the VT app. The health-store path is a chain of four links, wearable, maker's app, health store, VT, and each link has to run before the next can: the ring talks to its app when the app is opened or in the background when the phone allows it, the app writes the store, and VT reads the store when you open it. A VT device talks to the app over Bluetooth and needs nothing else. A continuous glucose sensor has its own routes, set out on the CGM entries: LibreLinkUp, Nightscout, or a direct service.

## Why you sometimes have to sync first

Because of the chain. A ring that has not spoken to its app since last night has written nothing to the store, so VT has nothing to read; opening the maker's app first lets the ring sync, the app write, and VT find it. When a night is missing in VT, the health store shows whether the maker's app ever wrote it, and that tells you which link failed.

## What makers write, and withhold

The health store merges every device into one stream, and VT reads from it the source you chose for each part of the app, so a part never mixes two devices. Some makers write less to the store than their own apps show: sleep stages, temperature, heart rate variability and the device's own scores are the usual omissions, and a direct connection usually brings more than the store does. VT shows you what your devices write during setup, and there is nothing VT can do about what a maker withholds. A reading that arrives by two routes, direct and through the store, is counted once.

## What VT writes back

Your VT scale's weigh-ins, glucose, meals, blood pressure and water are written back to the health store, so the other apps on your phone see what you entered in VT.

## Switching devices

Different devices measure sleep differently, so VT ties your sleep readings and overnight heart rate to the device that records them. A one-off swap, a watch while the ring charges, is set aside for that night; a real switch is accepted after the new device has recorded seven nights in a row, and VT then rebuilds your sleep normal from it, so about a week of results goes missing. Alternating from night to night keeps resetting this. Breathing rate, blood oxygen and temperature can also shift with a device change; expect a few unsettled days.

## Typing it in

Most measures can be typed, on the web or in the app; in the app, weight, body fat, glucose, ketones, blood pressure, meals, water, alcohol, bowel movements, your period and sick days. A typed value is never lost: it stays on record with when and where it was entered.

| Route | Devices | When something is missing |
| --- | --- | --- |
| Direct connection | Oura, Withings, Polar, Fitbit; LibreLinkUp (FreeStyle Libre); Nightscout (Ottai); the Sibionics service | Open the maker's app and let the device sync; allow up to an hour; check the connection is still authorized in VT's settings |
| Health store | Apple Health, Health Connect, Samsung Health, and any device whose app writes to them | Open the maker's app first; then check the store shows the reading; then open VT |
| Bluetooth | The VT scale, band and ring, and a Polar H10 strap | Keep the phone near; open VT with Bluetooth on |
| Typed | Anything | Nothing to sync; the value is there when you save it |

## Sources

1. Vitality Tracker, How it works (the sync paths, switching devices, what VT writes back); the engine catalogue of 15 October 2026 (the data sources; how VT keeps the record); the CGM page (sensor routes); Knowledge Base brief, how-to 4.

## Related

- [A scale and a band is a complete setup](https://vitalitytracker.app/knowledge/a-scale-and-a-band)
- [Bioimpedance: the smart scale](https://vitalitytracker.app/knowledge/bioimpedance)
- [What a CGM measures](https://vitalitytracker.app/knowledge/what-a-cgm-measures)
- [Night Log](https://vitalitytracker.app/knowledge/night-log)
- [Device sleep score](https://vitalitytracker.app/knowledge/device-sleep-score)
- [Same time, same way](https://vitalitytracker.app/knowledge/same-time-same-way)

Reviewed October 2026 · v1

Source: https://vitalitytracker.app/knowledge/how-your-data-reaches-vt