Polar
Polar Flow and Apple Health: what syncs, and what doesn’t
Switch on Apple Health in Polar Flow and you would expect everything your watch measures to turn up in the Health app. It doesn’t. Your workouts, steps and the times you fell asleep and woke up arrive. Your sleep stages, your all-day heart rate, your HRV and most of what makes a Polar watch worth wearing overnight stay inside Polar Flow.
Short answer
Polar Flow writes seven kinds of data to Apple Health: workouts, heart rate during workouts, active energy, resting energy, steps, weight, and sleep duration (when you fell asleep and woke up). It does not write sleep stages, continuous 24/7 heart rate, HRV, breathing rate, SpO2 or temperature, and Polar-only scores like Nightly Recharge have no place in Apple Health at all. To fill the gap you need a second app that reads Polar’s official API and writes the missing types.
What Polar Flow writes to Apple Health
Polar publishes the list on its own support page. This is everything Flow sends when the Apple Health switch is on:
| Data | What arrives in Apple Health |
|---|---|
| Workouts | Sport, duration, distance, start and end time, total calories and average heart rate |
| Heart rate | Only during workouts. Polar states that continuous heart rate is not synced |
| Active energy | Calories burned in workouts |
| Resting energy | Calories burned outside workouts (BMR) |
| Steps | Your daily step count from the watch |
| Weight | The value saved in your Polar Flow settings |
| Sleep | Duration, time asleep and time awake, as one block without stages |
The sync is one way. Polar Flow writes to Apple Health but reads nothing back, so workouts recorded on an iPhone or another watch never show up in Flow.
What stays behind in Polar Flow
Apple Health has a place for most of the missing data. It simply isn’t sent:
| Measured by your Polar | Apple Health has a type for it | Sent by Polar Flow |
|---|---|---|
| Sleep stages (light, deep, REM, awake) | Yes: Core, Deep, REM, Awake | No |
| 24/7 heart rate | Yes: Heart Rate | No, workouts only |
| Breathing rate during sleep | Yes: Respiratory Rate | No |
| Blood oxygen (SpO2 test) | Yes: Blood Oxygen | No |
| Temperature | Yes: Body Temperature | No |
| HRV (RMSSD, from Nightly Recharge) | Only as SDNN, a different measure | No |
| Nightly Recharge, ANS charge, sleep score | No | No |
| Cardio load, muscle load, Running Index | No | No |
That leaves two different problems. The first five rows are a sync gap: the data has a home in Apple Health and only needs to be written there. The last three rows have no Apple Health type at all, so no app can put them into the Health app. They have to be kept somewhere else if you want them for longer than Polar shows them.
Turn on the sync Polar Flow does offer
Start with Polar’s own integration, because it covers workouts and steps:
- Open the Polar Flow app on your iPhone and tap More.
- Go to General settings and switch on Apple Health.
- Allow the data types when iOS asks. New data then syncs every time Flow syncs with your watch.
Only data that arrives after you switch it on is sent. Older workouts stay in Polar Flow.
Get sleep stages, 24/7 heart rate and the rest into Apple Health
Polar offers an official API, AccessLink, that apps can use with your permission. It serves the data Flow leaves out, so an app built on it can write the missing types into Apple Health. Keho is one of them. With it the setup takes a minute:
- Install Keho and allow access to Apple Health.
- In Keho, connect your Polar account. You sign in on Polar’s own website; Keho never sees your password.
- Choose what to sync: sleep stages, 24/7 heart rate, breathing, SpO2, temperature, and whether Keho or Polar Flow should write your workouts.
From then on Keho syncs in the background, overnight and whenever you open it. Every sample it writes carries a sync identifier, so running the sync again updates entries instead of doubling them, and data from other apps is never touched. In the Health app you then see Polar sleep with stages (Polar’s light sleep appears as Core), an all-day heart-rate chart, and respiratory rate, blood oxygen and body temperature from your Polar.
Keho also keeps the Polar-only numbers that Apple Health can’t hold, such as Nightly Recharge, ANS charge, sleep score and cardio load, in storage on your iPhone, so they build up into long-term trends. Other tools can move Polar data too: Health Sync by appyhapps is a general-purpose sync app that covers Polar among other services. Check its current list of supported data types before you choose.
A note on HRV
Polar measures heart rate variability as RMSSD during the first hours of sleep and reports it inside Nightly Recharge. Apple Health’s HRV field expects SDNN, which is what Apple Watch records. The two are different calculations and their values aren’t interchangeable, so copying a Polar RMSSD value into Apple’s SDNN field would put wrong numbers into your Health history. Keho therefore keeps Polar HRV as RMSSD and shows its trend in the app. Why SDNN and RMSSD differ.
History older than four weeks
Polar’s API only serves roughly the last 28 days. Anything older has to come from Polar’s full data export, which you can request from your Polar account and import into Keho. How to export your Polar data and keep your history.
Common questions
Does Polar Flow sync sleep stages to Apple Health?
No. Polar Flow sends sleep as one block with a start and end time. Stages only reach Apple Health through an app that reads Polar’s API, such as Keho.
Does Polar sync HRV to Apple Health?
No. Polar Flow doesn’t write HRV, and Polar’s RMSSD value doesn’t match the SDNN measure Apple Health stores anyway.
Can Apple Health data go into Polar Flow?
No. Polar’s integration only writes to Apple Health; it doesn’t read from it.
Which Polar watches does this work with?
Any device that syncs to a Polar Flow account, including the Vantage, Pacer, Grit X and Ignite families, Verity Sense and the H10 and H9 straps. Which data exists depends on the device: SpO2 and temperature, for example, come only from watches that measure them.
Source: Polar support, “Connecting Polar Flow with Apple Health”, checked on 28 September 2026. Keho is an independent app and not affiliated with Polar Electro Oy.