Insulin is the main regulator of sugar in the bloodstream.
This hormone is manufactured by beta cells and continuously released into the bloodstream. Beta cells are found in the pancreas, which is an organ behind the stomach. Insulin levels in the bloodstream are carefully calibrated to keep blood glucose just right.
High insulin levels push sugar out of the bloodstream, into muscle, fat and liver cells, where it is stored for future use. Low insulin levels allow sugar and other fuels to be released back into the bloodstream.
During the night and between meals, insulin levels in the bloodstream are low and relatively constant. These low insulin levels allow the body to tap into its stored energy sources (mainly glycogen and fat) and also to release sugar and other fuels from the liver. This insulin during the night or between meals is called background or basal insulin. When you have not eaten for a while, your blood sugar level will be somewhere between 60 to 100 mg/dl.
When you eat, the amount of insulin released from the pancreas quickly spikes. This burst of insulin that accompanies eating is called bolus insulin. After a meal, blood sugar levels peak at less than 140 mg/dl and then fall back to the baseline (pre-meal) level. High insulin levels help sugar to leave the bloodstream and be stored for future use.
There are other hormones that work together with insulin to regulate blood sugar including incretins and glucose counter-regulatory hormones, but insulin is the most important.
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