For the second time since it announced its HealthKit plans, Apple has made a mistake related to blood glucose measurement units. Last week the company pulled the glucose tracking feature out of its Health app for users in some countries where glucose is tracked in millimoles per liter (mmol/L) and not milligrams per deciliter (mg/dL) like they are in the US.

"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," Apple wrote in its support forum a few days ago. "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." 

Apple continued: "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. However, your data won't be deleted, and other apps with permission to read health data will still have access to blood glucose values that you previously entered."

During its presentation at WWDC earlier this year, Apple -- or its partner Epic Systems -- had a typo in its slide about glucose tracking.

As we reported at the time: Rock Health published a blog post reaction to HealthKit written by the sharp-eyed Aaron Rowe, research director at Integrated Plasmonics, who noticed that one of the slides Apple presented during the event had the wrong measurement units for blood glucose monitoring. The slide (pictured at the bottom of this post) listed them as mL/dL, while the correct units are mg/dL. The error was actually part of a screenshot of Epic’s MyChart app so it may have been Epic’s mistake, but it was part of an Apple executive’s presentation. For a company long known for its attention to detail, not a great indicator for how deep Apple’s medical bench is.

A typo on a slide at a major launch event is embarrassing. But an error like Apple's most recent one, where patients with diabetes in countries like Australia or the UK may be relying on their health apps for an accurate number -- one that will likely affect dietary decisions they make -- has much higher stakes.