How These Simulators Work

Food, insulin, and exercise all operate at different speeds — and those change when they overlap. These tools make those invisible processes visible so you can learn to anticipate them.

What You're Looking At

Each chart shows relative effects — how a factor moves blood sugar compared to a flat baseline. No actual blood sugar numbers appear, because everyone's starting point is different. The shape of the curve is what matters: when it peaks, how long it lasts, and how it overlaps with other effects.

Not medical advice. These are learning tools, not management tools. Talk to your care team before making any changes to your insulin or exercise routine.

Each simulator is a sandbox for one concept. Start with the individual simulators to build intuition for each effect. When you're ready, the 24-Hour Simulator lets you combine everything and see how they interact across a full day.

What each toggle shows

The buttons above each chart let you show or hide individual effects. Here's what each one represents.

Carb Effect

Food raises blood sugar

Carbohydrates digest into glucose and enter the bloodstream. Fast-absorbing carbs (juice, glucose tablets) hit quickly. Complex carbs, fat, and protein slow the process down — which is why the same amount of food can produce very different curves depending on what's in it.

Insulin Effect

Insulin lowers blood sugar — slowly

Fast-acting insulin starts working about 10-15 minutes after injection, peaks around 60-90 minutes, and stays active for up to 6 hours. It never acts instantly. Where you are in that curve when you eat or exercise changes everything.

Basal Effect

Background insulin rate (pump only)

Insulin pumps run a continuous background dose all day. A temp basal change — higher or lower — takes 60-90 minutes to reach full effect. What you see is how that change compares to your normal baseline rate.

Exercise Effect

Muscles pull glucose during a workout

During aerobic exercise, working muscles absorb glucose directly from your blood — without needing insulin to do it. Blood sugar drops during the workout, and the drop is faster if insulin is also active. Harder effort means faster glucose uptake.

Post-Ex Effect

Recovery pulls glucose for hours after

After a workout ends, your muscles and liver continue pulling glucose from the blood to replenish depleted stores. This can last up to 24 hours. It's the main reason meals after a hard workout often need less insulin than usual — and why overnight lows happen on workout days.

Dawn Effect

Morning hormones raise blood sugar every day

Each morning, cortisol and growth hormone signal your liver to release stored glucose to fuel the start of the day. In people without diabetes, the pancreas compensates automatically. Without that response, blood sugar rises predictably every morning — whether you eat or not.

Overnight Sensitivity

Exercise makes insulin more effective overnight

After significant exercise, your body becomes more sensitive to insulin during sleep — the same dose lowers blood sugar more than it normally would. The harder you worked that day, the stronger the effect. It's one of the most common causes of unexpected overnight lows on workout days.

The Four Main Drivers of Blood Sugar

Understanding what moves blood sugar — and how fast — is the foundation of everything in these simulators.

Insulin

Insulin is what lets your cells use glucose for energy. Fast-acting insulins — sold as Humalog (lispro), Novolog (aspart), and Fiasp (faster aspart) — take time to work and stay active for hours. Long-acting insulins — Lantus/Basaglar/Toujeo (glargine), Levemir (detemir), Tresiba (degludec) — provide a slow background throughout the day. Insulin pumps use only fast-acting insulin for both background and meal doses.

Your body needs some insulin at all times — not just when blood sugar is high. Without it, cells can't use glucose and begin burning fat instead, producing acidic byproducts called ketones. When ketones accumulate too fast, it becomes life-threatening (diabetic ketoacidosis, or DKA). DKA is caused by too little insulin, not high blood sugar — it can develop even when glucose looks normal, especially for pump users who suspend insulin for extended periods.

Carbohydrates

Carbohydrates raise blood sugar by converting to glucose during digestion. Speed depends on the type — pure sugars absorb in minutes, complex carbs take much longer. Fat and protein slow digestion, so a high-fat meal produces a very different curve than a bowl of rice with the same carb count. Fast-acting carbs (glucose tablets, juice) are the right tool for raising a low quickly — complex food is not.

Exercise

Exercise lowers blood sugar by allowing muscles to absorb glucose directly, without insulin. It also increases insulin sensitivity for hours afterward. High-intensity exercise works differently — stress hormones cause the liver to dump glucose, temporarily raising blood sugar during the effort before the drop comes later.

Your Liver

Your liver stores glucose as glycogen and can release it into the bloodstream when the body signals it to. Two different mechanisms trigger that signal. The first — stress hormones like adrenaline during intense exercise or cortisol during illness or anxiety — still works in T1D and is a major reason blood sugar can rise unexpectedly without any food or insulin changes. The second is glucagon, a hormone the pancreas releases specifically in response to low blood sugar, which prompts the liver to release glucose as a rescue. In people without T1D, this rescue works automatically. In T1D, beta cells are destroyed, disrupting the signal that triggers glucagon — so the automatic rescue from hypoglycemia is significantly impaired or absent, particularly in people who have had T1D for many years. This is one of the reasons low blood sugar in T1D often requires eating fast carbs, glucagon nasal spray, or an injection to treat, rather than the body correcting itself.