Your body runs on the sugar that is always present in your blood stream. The concentration of glucose in your blood varies throughout the day, rising after meals and falling between them. The length of time it takes for your blood sugar level to peak after eating depends on the type and quantity of food you eat and your body's ability to produce insulin. It can be anywhere from 15 minutes to several hours.
Your Body's Fuel
Humans, like all animals, depend on glucose in their blood streams for fuel. Glucose is the simplest of sugar compounds that your body oxidizes and converts into water and carbon dioxide to release energy. If the amount of available sugar is too low, your body will burn fat and in the absence of fat it can run on protein, but its preferred fuel is glucose.
Digestion
The sugar in your blood can come from a number of different sources. It might be from foods that contain glucose or other sugars, but your body produces most of its blood sugar from more complex carbohydrates and other compounds. All the sugar from digestion goes immediately into the blood until used or stored as other compounds.
Blood Sugar Levels
Your blood sugar level should remain at a fairly constant level unless you are eating. An average serum glucose level when you are not digesting is about 85 mg per deciliter of blood. Shortly after a meal or snack that level rises. In a healthy person the peak sugar level will normally occur from 30 minutes to two hours after eating, depending on the food consumed, with the average being one hour.
What You Eat
The quantity and type of foods that you eat determine when the peak sugar level occurs. Eating a sugary doughnut on an otherwise empty stomach will produce a different result than a full meal containing fats, proteins and complex carbohydrates. The doughnut will produce a higher peak in a shorter amount of time. If you were to consume pure glucose, a peak could occur in as little as 15 minutes; while eating slower digesting foods, it may be as long as three hours.
The Control Mechanism
If you are an average adult your blood contains a total of only 4 g of glucose. When you eat a meal your digestive system introduces an amount of glucose that is much larger than this total. Without some way of burning off or storing the sugar, the glucose would rise to a dangerous level. Your body produces insulin to help control blood sugar and keep it within acceptable limits.
Diabetes
Diabetics do not release a sufficient amount of insulin to control their blood sugar. If you are diabetic, it takes longer for your blood sugar to peak after eating and the value can reach higher levels. While a normal person's glucose level would peak in 30 minutes to one hour after a meal, a diabetic may not reach a peak level for one to two hours.
