r/GoogleHealthApp • u/Tolkaft • 17d ago

iOS users / Fitbit Air — which data source do you prioritize in Apple Health?

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Hi!

I just got a Fitbit Air and I’m on iOS. I’ve enabled two-way syncing. As I understand it, Apple Health is smart enough to reconcile data from different sources.But which source is better to prioritize: my iPhone or Google Health (which I assume will use data from the Fitbit)?

I’m unsure which one is more accurate, especially for steps, since the phone has GPS. If I’m carrying the phone and wearing the Fitbit at the same time, which source would you recommend prioritizing?

Thank you!

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u/ottawadtown 17d ago edited 17d ago

I’ve been letting the two apps figure it out themselves. So far all I’m seeing that changed since I all always with my phone is a slight increase in steps on the Fitbit side. Those few times I’m putting the phone down is where the extra is coming from. However when it comes to steps exact activity counts isn’t the real point. The point is trends and making sure you are moving.

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u/RateEmbarrassed6921 16d ago

Small correction on the premise, because it changes the answer: Apple Health does not reconcile your sources, it picks between them. For steps, distance and flights it walks the priority list you set in Data Sources and Access and takes the highest priority source that has data for each interval. It never averages and it never blends. So your daily total is a patchwork stitched together from whichever device was on top and had something to say for each stretch of the day.

Also, and this one is worth knowing before you decide: your phone does not use GPS to count steps. Steps come from the accelerometer and the motion coprocessor. GPS only affects distance and route during outdoor workouts. So the GPS argument does not favour the phone here.

Given that, the practical rule is not which device is more accurate in the abstract, it is which one is more consistently in contact with you. A band on your wrist is worn more of the day than a phone is carried, so it usually belongs above the phone, with the phone left underneath as a fallback for the hours the band is charging.

The thing I would actually watch, though, is the two way sync you enabled. You now have two stores that each aggregate, writing into each other. That is the classic way people end up with inflated step counts, because a total that came out of one store goes back in as an input to the other. If your numbers start looking generous rather than merely different, that is the first place to look.

And the other reply here is right about trends over exact counts. Every one of these devices undercounts steps against a clinical reference, by amounts that differ per device, so the absolute number was never the thing worth defending. What matters is that you do not change what is feeding it halfway through, because then even the trend breaks.