gluCal: The all-in-one calculator and log to simplify insulin dosing

1. Insulin Calculator

Users input their current glucose levels and carbohydrate intake then select a carb ratio. gluCal then calculates the recommended insulin dose based on their personalized settings, which can be adjusted at any time. Users can also log specific foods along with the carb count.

2. Insulin Log

All insulin calculations are automatically stored in the insulin log. Users can also add logs manually from this page for doses taken without using the calculator for more flexibility.

3. Food Diary

The food diary logs all food items entered through the insulin calculator to help users track their diet alongside their insulin intake. Users can also create a food diary entry directly from this screen.

To start, I conducted 3 user interviews with people with Type 1 Diabetes, and identified 2 main pain points.

Question·How might we make calculating insulin doses easier and less frustrating for people with diabetes?

I conducted a competitive analysis and discovered that existing solutions varied along 2 key spectrums: visual design and scope.

Finding·Existing diabetes tools fall short for users seeking a simple, focused solution, without the complexity of broader management systems.

I started off by exploring different layouts and mapping out the basic app structure on paper.

How do we show that logging food is associated with the carb count input?

Users have the option to log the food they’re eating when calculating insulin. If a user logs food, the carbs input field is automatically filled with that information.

The “log food” button needed to appear 1. optional and 2. associated with the carbs input field.

1. Attached, outline

2. Attached, solid

3. Separate, outline

4. Separate, solid

	1	2	3	4
Perceived optionality	Outline creates lower hierarchy, signaling optionality	Set apart by position, but unclear without a label	Outline differs from mandatory fields, but shape is unchanged	Unclear as optional without a label
Association to carb input	Near the carbs input, but connection unclear	Near the carbs input, but connection unclear	Positioned separately, no evident relation	Positioned separately, no evident relation

However, users still expressed that logging food seemed like a separate process from inputting carb amounts.

One user suggested to nest the button within the carb input field. When the button is nested within the field, it visually indicates that the log food action is part of the carbs input process, rather than a separate action that is simply associated with carbs.

Nested button

	5
Perceived optionality	Outline creates lower hierarchy, signaling optionality
Association to carb input	Nesting shows logging food is an optional way to input carbs.

Perfect! This was a great solution that I would not have come up with without the help of user feedback!

What would it look like to log multiple food items at once?

When logging food from the calculator, an intermediate screen appears that stores all the food the user is logging. I explored two different approaches for the food input form that appears after they click “Add Item”.

How should we structure the data synchronization of the insulin log and food diary?

When a user logs food alongside an insulin calculation, two entries are created — one in the insulin log, one in the food diary — connected by a shared carb count. If that carb count is edited later in one log, should it update the other, and should the associated insulin dose update too?

I weighed this against two priorities for gluCal: simplicity (the app should reduce thinking, not add to it) and flexibility (real life is messy — people don’t always log insulin and food together, or in order).

Keeping the carb counts independent supports both: users can edit either log without triggering unexpected changes elsewhere, and it avoids the technical complexity of syncing data across gluCal’s two separate database tables.

Decision·Carb counts stay independent across the insulin log and food diary.