High blood glucose after meal but not high fasting is a manifestation of abnormal blood glucose condition, and the main reasons include abnormal diet, lack of exercise and insufficient insulin secretion. 1. Dietary abnormalities: large amounts of carbohydrates consumed during meals can lead to large amounts of blood glucose being absorbed into the bloodstream, resulting in high postprandial blood glucose. 2. Lack of exercise: too little exercise after meals will also affect the metabolism of blood glucose in the body, thus causing postprandial blood glucose to rise. 3. Insufficient insulin secretion: Insufficient insulin secretion is the main cause of high blood sugar after meals, which is caused by the decline of pancreatic function or insulin resistance. If you have obvious postprandial blood glucose elevation and can’t control it through diet and exercise, you need to consult a doctor in time, get a clear diagnosis, and standardize the treatment under the doctor’s guidance, so as to avoid delaying the condition.