Glucose pump application ● Eversense
I redesigned a mobile app for Eversense’s first permanently-implanted glucose sensor. The app quickly received FDA approval.
In use, the app first had to assist the user in first positioning an external transmitter over the implanted sensor.
Then the app had to provide blood sugar status and recommendations to patients with little technical or scientific background.
Linear vs. logarithmic scale?
A big issue was how to glucose values. A person with diabetes ideally maintains a glucose level between 70 mg/dl and 180 mg/dl. A critical low is around 40 mg/dl, but readings can be as high as 400 mg/dl. The design requirement was to display a range between 50 and 400 mg/dl.
A purely linear numeric scale (on the left) topping out at 400 mg/dl and scaled to a mobile screen would have looked very bottom-heavy since most readings would be clustered within the bottom 50% of the scale. I solved the problem by using a logarithmic scale (on the right). The ideal target range was vertically centered on the screen and the upper and lower ranges were approximately the same size.
I argued that patients didn’t need to know whether the scales were linear or logarithmic. They simply needed an indicator to show the latest glucose measurement.