Same meal, different reading—what happened?

You eat the same rice and chicken as a friend, then compare readings. The numbers look nothing alike. It can feel unfair or as if one of you has done something wrong.

Blood sugar responses are often discussed as though every meal should produce one predictable result. But bodies are not identical calculators, and food does not arrive in an empty laboratory. The same meal can affect two people differently—and may even affect the same person differently from one day to the next. The main idea to remember is simple: a reading reflects the meal and the circumstances around it.

Carbohydrates in foods such as rice, bread, potatoes, oats, beans, fruit, and milk are broken down into glucose, which can raise blood sugar. But how quickly and how much it rises depends on many things. Digestion speed, insulin production, insulin resistance, medication, physical activity, stress, sleep, illness, hormones, and the timing of the meal can all play a part.

Even meals that look identical may not truly be identical. One plate may contain a little more rice, a larger piece of bread, or a sweeter piece of fruit. Cooking and preparation can matter too: a soft, well-cooked starch may be digested differently from a firmer version. Adding beans, eggs, fish, chicken, yoghurt, vegetables, or another source of protein, fat, or fibre may also slow digestion for some people.

This does not mean you need to calculate every ingredient or turn lunch into a science project. It means another person’s response cannot tell you exactly what your body “should” do. Their medication, activity, sleep, and underlying biology may be very different from yours.

The same is true when comparing yourself with yourself. Perhaps a familiar breakfast gives you a higher reading on a morning after poor sleep. A meal after a walk may produce a different result from the same meal eaten during a stressful day at a desk. One surprising number does not prove that the meal is forbidden or that your diabetes is suddenly getting worse.

If you want to understand a meal better, try a small, low-cost experiment. Choose one ordinary meal you eat regularly—perhaps oats and yoghurt, rice with beans and vegetables, or bread with eggs. On two or three occasions, check your blood sugar at the times recommended by your healthcare team. Make a brief note of the portion, activity, sleep, stress, and medication timing.

You are not trying to recreate perfect conditions. You are looking for a repeated pattern. If the response is usually higher than your agreed target, consider one manageable change, such as slightly reducing the starch portion or adding more beans, vegetables, eggs, fish, or chicken. Then observe again rather than changing everything at once.

Repeated unexpected highs or lows deserve a conversation with your healthcare team, especially if you feel unwell or are unsure how your medication fits with meals. Do not change medication based on another person’s readings or one isolated result.

Your blood sugar response is personal, not a competition. This week, choose one familiar meal and observe it twice with a little context. The goal is not to earn a perfect number. It is to learn what tends to work for your body, in your real life.

Until next week,
Michael

PS: We’re building Cocoa, a diabetes food companion designed to help you notice how everyday meals and real-life circumstances connect—without judging a single reading. If you’d like to help us test it, reply to this email. Testing spots are limited while we learn closely from each person.