With the upcoming public release of iOS 8.2, iPhone and iPad users will note the return of glucose tracking to the Health app.

In October, Apple removed blood sugar measurement from the app because it offered only one unit of measurement — mg/dL (milligrams per deciliter). This is commonly used in the U.S., but another unit — mmol/L (millimoles per liter) — is used in Europe, and Apple has since added it to the Health app.

The publicly available version of iOS 8 has no blood sugar tracking in the Health app, but Apple has released a beta version of iOS 8.2 and it includes blood glucose measurement.

But Apple has had trouble with blood sugar tracking. This may have stemmed from a basic misunderstanding of how blood sugar level is measured around the world. (When Apple announced the Health app last spring, VentureBeat discovered that one of the slides held an error in the blood sugar measurement metrics.)

Here’s what Apple said in its developer forum when it first pulled blood glucose from Health:

“If you measure your blood glucose using a device that displays mmol/L, those values can’t be manually entered or displayed in the Health app with that unit of measurement. To prevent confusion in countries where mmol/L is commonly used, we’ll soon release a software update that will temporarily remove the ability to manually enter and view blood glucose values in the Health app while we work on an update to support both units of measurement.”

Why is this important? Blood sugar is related, in a general way, to the most costly of all health problems, obesity, and more specifically to diabetes.

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