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How do insulin and glucagon keep blood glucose levels stable?

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human endocrine system The principal glands of the female and male human endocrine systems.

The human body maintains stable blood glucose levels through a delicate homeostasis mechanism involving two primary hormones secreted by the islets of Langerhans in the pancreas: insulin and glucagon.12

Insulin is secreted by beta cells when blood glucose levels rise. It lowers blood sugar by:
* Promoting the uptake of glucose into muscle and adipose cells.1
* Encouraging the liver to store excess glucose as glycogen.1
* Decreasing gluconeogenesis, the production of glucose from non-carbohydrate sources.1

Glucagon is secreted by alpha cells when blood glucose levels are low, such as during fasting or exercise. It acts in direct opposition to insulin to raise blood sugar by:
* Stimulating glycogenolysis, the breakdown of stored glycogen into glucose in the liver.32
* Promoting gluconeogenesis to generate new glucose.3

Together, these hormones function through a negative feedback system, ensuring that glucose concentrations remain within a narrow, healthy range.1