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24-Hour Diabetes Simulator

See how food, insulin, and exercise interact across an entire day — and how decisions made in the morning shape what happens at night.

Every simulator on this site isolates one variable at a time — a single bolus, one workout, a temp basal change. In real life, all of those things happen on the same day, and the effects compound in ways that aren't always intuitive. A workout at noon changes how your evening meal behaves. A temp basal set hours before exercise still has insulin on board during it. Multiple workouts mean glycogen depletion carries forward from one session to the next.

This simulator lets you build an entire day from scratch using the same underlying math as all the other simulators. Add boluses, meals, exercise sessions, and (if using a pump) temp basals at any time in the 24-hour window. The effects stack and compound exactly as they would in your body.

New here? If the chart looks overwhelming, start with the individual simulators to learn each effect in isolation — then come back here to practice combining them.

Pay attention to:

For educational purposes only. This simulator is a visual learning tool — not a medical device or dosing calculator.

What's happening here?

The chart shows blood glucose effects across a full 24-hour day, from your selected wake time back to the same wake time the next day. The darker shaded region is your sleep window. The chart starts flat — all the BG change you see comes from entries you add.

Dawn phenomenon

Starting at wake time, cortisol and growth hormone naturally drive the liver to release glucose — a phenomenon called the dawn effect. In people with type 1 diabetes, there is no automatic compensating insulin response, so BG rises predictably each morning. The size of the rise varies by person, but it is nearly universal. Most people need to account for this with a morning bolus or, on a pump, a higher pre-dawn basal rate.

Compounding exercise effects

When you exercise more than once in a day, the effects stack. The post-exercise sensitivity from your first session may still be active when your second workout begins. More importantly, glycogen stores depleted during the first workout have to be replenished through food before the next session — otherwise your muscles are drawing from an already-depleted reserve, making the blood sugar drop during exercise larger and faster than expected.

Overnight insulin sensitivity

Research consistently shows that moderate-to-heavy exercise increases insulin sensitivity for 12-24 hours afterward, including during sleep. For people on insulin, this means the same basal rate that kept blood sugar stable the night before a workout day may cause low blood sugar the night after. The effect is proportional to how much you exercised — a light 30-minute walk has minimal effect, while a hard hour-long run or a long bike ride can meaningfully shift overnight sensitivity.

MDI vs Pump

MDI users have long-acting basal insulin that cannot be adjusted once injected — the only tools are timing and amount of fast-acting doses, and food. Pump users can add temp basals at any point to adjust delivery up or down, giving more flexibility around exercise, meals, and overnight patterns.

Applying this to your own life

The goal of the individual simulators is to help you understand each effect in isolation. The goal of this one is to help you understand how they interact. Use them in that order.

  • Start with the individual simulators: Use Bolus Timing, Split Bolus, Exercise Timing, and the others to build intuition for each effect in isolation — then come back here to practice combining them. If you see something in the 24-hour chart you don't understand, open the specific simulator for that effect.
  • Match the simulator to your day: Think of a real day you've had — a workout, a meal that didn't go as expected, a late correction bolus — and try to recreate it here. See if the chart reflects what you actually experienced.
  • Keep notes: When you notice a pattern in your own data — lows on workout evenings, a stubborn high every morning — bring that question to the simulator. Try different combinations and see what the model suggests.
  • Try things you wouldn't try in real life: This is a simulation. Setting a temp basal two hours before exercise and seeing how it plays out costs nothing here. Build the intuition before you need it.