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How do insulin and glucagon regulate blood glucose levels?

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Diagram showing the locations of major human endocrine glands in male and female bodies, including pineal gland, hypothalamus, pituitary gland, parathyroid glands, thyroid gland, thymus, adrenal glands, pancreas, kidneys, testes, and ovaries. — Endocrine system The glands of the human endocrine system.

Insulin and glucagon are hormones produced by the islets of Langerhans in the pancreas that work in opposition to maintain blood glucose homeostasis.12

Insulin

Secreted by beta cells, insulin acts to lower blood glucose levels. It facilitates the uptake of glucose into muscle and adipose tissue and promotes the storage of excess carbohydrates as glycogen in the liver. Additionally, insulin inhibits gluconeogenesis, the production of glucose from non-carbohydrate sources, further reducing blood sugar.321

Glucagon

Secreted by alpha cells, glucagon is a hyperglycemic hormone that raises blood glucose levels, particularly during fasting or exercise. It opposes insulin by stimulating glycogenolysis—the breakdown of stored glycogen into glucose—and by promoting gluconeogenesis in the liver.143

These hormones operate through a negative feedback mechanism: high blood glucose triggers insulin release to lower levels, while low blood glucose stimulates glucagon release to restore balance.12