How and When Glucose Rises After a Meal (Postprandial Glucose Explained)
In the morning, the measured glucose level is at a minimum. For this reason, doctors recommend going to the laboratory between 7 and 9 a.m. Glucose levels rise after a meal, and this rise is called the postprandial spike, which is explained in detail when discussing normal blood glucose levels. Glucose spikes and drops depend on the type and size of the meal.
What Foods Cause Blood Glucose Spikes?
For example, foods with fast-digesting carbohydrates and little fiber and protein (bread, rice, cakes, cereal, soda, etc.) raise the glucose level sharply after ingestion. They are not considered nutritionally useful for regular meals. On the other hand, it is a very useful “fuel” for more strenuous physical activities. During a glucose measurement at mealtime, a sudden spike in glucose to higher values occurs, followed by a drop. In the situation of consumption of carbohydrates after physical activity, a mild increase in glucose is observed.
Why Protein, Fiber, and Fat Stabilize Blood Glucose?
Food with protein, fiber, and fat slows down absorption and thus does not cause sudden spikes in glucose. For example, eggs, meat, fish, vegetables, nuts, and legumes are nutritionally rich foods. During the measurement, no sudden spike in glucose appears, and the drop is gradual.
Timing of Postprandial Glucose Peak and Decline
The beginning of the increase in glucose occurs at the beginning of food intake.
The postprandial peak of glucose values is expected in a period of 30 to 60 minutes. It depends on the type of food ingested. (Source)
Sample Meals and Their Realistic CGM Glucose Responses
❌ An example of food and drink that quickly raises the level of glucose and keeps it high:
- Coca-Cola, crisps, Milka chocolate, macaroni, Nutella, Guarana, fruit juices, figs, and other industrially processed food and drinks
✅ An example of food that does not quickly raise glucose or is suitable for consumption after physical activity:
- Nutrino Lab, bananas, Benlian Choco Slim, Protein Go On Granola, Avocado, boiled chicken, tuna, boiled eggs, vegetables
A decrease in glucose is expected within 2 hours from the time of food intake to approximately initial values. In general, absorption of food takes about 4 hours, but the drop in glucose occurs earlier. (Source)
👉 Next: How Physical Activity Affects Blood Glucose Levels?
The goal of this personal glucose monitoring experiment is to understand long-term trends rather than single values. For a complete overview, visit the CGM data–based educational series.
