Blood insulin increases after a meal because food triggers the release of insulin from the pancreas. Insulin is necessary for the body to properly regulate blood sugar levels. When food is consumed, the carbohydrates are broken down into glucose, which enters the bloodstream. In response to the rising blood glucose levels, the pancreas releases insulin to signal the body's cells to take in and use the glucose for energy or store it for later use. This helps to lower blood sugar levels back to normal levels after a meal.
