Postprandial blood sugar is a measurement of the glucose concentration in your bloodstream in the period up to 4 hours after eating a meal. When you eat, your body breaks down carbohydrates from foods into simple sugars, glucose and fructose, which are absorbed into the bloodstream.
We can break up our body’s state into 3 metabolic periods:
- Postprandial: The first four hours after eating or drinking. Complex carbohydrates and simple sugars are absorbed into the bloodstream and lead to an increase in blood glucose. Blood glucose begins rising within a few minutes of eating, but the duration of absorption is around four hours.
- Postabsorptive: This period occurs for about four to six hours following the postprandial period. The liver breaks down glycogen, the stored form of glucose, to keep blood sugar levels relatively stable.
- Fasted: After the postabsorptive period (about 10-12 hours after eating), your body is in a fasted state until your next meal. During this phase the body produces glucose through non-carbohydrate sources, such as lactate, through a process known as gluconeogenesis.
What are normal and high levels of postprandial blood sugar?
Typically, blood sugar levels peak between 1 and 2 hours after eating, when the carbohydrates in your food have been broken down into glucose — or sugar — and this has entered your bloodstream.
- A postprandial blood sugar measurement below 140 mg/dL (7.8 mmol/L) is considered normal.
- If your levels are between 140 and 199 mg/dL (7.8 and 11 mmol/L), it indicates that you may have prediabetes.
- A reading of 200 mg/dL ( 11.1 mmol/L) or higher suggests that you have diabetes, but your doctor may use more than one test to make a diagnosis.
For people without diabetes, there aren’t any guidelines for postprandial blood sugar levels when eating their normal diet. The thresholds that healthcare professionals use for making a diabetes diagnosis are specific to the OGTT test.