Apple has said that it will remove the ability to manually enter and view glucose values in its Health app, while the company comes up with a fix to allow HealthKit to handle the milligrams per decilitre (mg/dL) measurement of blood glucose levels used in the United States, as well as the standard millimoles per litre (mmol/L) used throughout the rest of the world.
First spotted by CNET, Apple said it is removing the manual entry function to prevent confusion.
"HealthKit supports both units of measurement," Apple said in a support note. "However, 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.
"If you have previously entered values manually in the Health app, you'll no longer see this data in the Health app after the update."
Cupertino said that user data will not be deleted, with third-party apps remaining able to read the data.
"Third-party apps will continue to be able to support both units of measurement and can continue to use HealthKit APIs to store blood glucose data," Apple said.
This episode is far from the first time that a US company has fallen foul of metric and imperial unit conversion, perhaps the most famous incident being NASA's Mars Climate Orbiter, which ploughed into the surface of the red planet after ground-based software produced output in pound-seconds, rather than the specified newton-seconds.
This meant that the thruster firings on the Orbiter were out by a factor of 4.45, the report (PDF) into the crash said.
The report recommended that NASA audit its software for the consistent use of units throughout spacecraft design and operation.