What it means
Beta cells in the pancreas release insulin when blood sugar rises, mainly after meals. Insulin lets muscle, fat and liver cells take in glucose, tells the liver to store it and slows the release of fat from fat cells.
In type 1 diabetes, the body makes little or no insulin. In type 2 diabetes, the body does not use insulin well, a problem called insulin resistance, and over time may not make enough of it.
GLP-1 medicines increase insulin release when blood sugar is high, which is why they lower blood sugar without usually causing lows on their own. The risk of low blood sugar rises when they are combined with insulin injections or certain other diabetes drugs.
Insulin is also a medicine used by many people with diabetes. Anyone who takes insulin should work with their care team before starting a GLP-1, since doses may need adjusting.
Why it matters
Insulin is the main hormone GLP-1 medicines act on to lower blood sugar.