If you test a meal under exactly the same conditions, you would roughly see the same pattern in glucose levels. However, these conditions are almost impossible to reproduce every day. A couple of things, why a meal can trigger sometimes a higher, or less high peak:

  • You ate something before the meal, that had an effect on your meal. Especially when this contained fats or fibers, which promote a slow release of blood sugars
  • You ate something after a period of fasting. This will create a peak in your blood sugar levels, in almost all cases
  • The meal was slightly different in composition. It is difficult to exactly construct the same meal (e.g., a curry is a complex dish of rice, meat, sauce and vegetables, so an interplay of fats, sugars and fibers)
  • A banana can be higher in sugars, when it has more brown spots
  • The portion size was larger or smaller
  • The time of the day might affect the inclination in blood sugar levels. An apple might spike more in the morning, than in the afternoon
  • How long do you take to complete your meal? This might influence the height of your sugar peak
  • Did you finish your entire plate, or left something uneaten?
  • With your meal, did you drink something differently (e.g., a glass of water vs. a can of Coke)
  • Sometimes, after a bad night of sleep, your glucose patterns can be more 'wobbly'
  • Did you take medication (or pain killers) with or after the meal? The pain killer typically won't influence your blood sugar levels, but can reveal a different cause of elevated glucose levels (like an illness)