Blood glucose homeostasis is a control system centered on the pancreas and liver, with muscle and fat acting as major fuel users/stores.

After a carbohydrate-containing meal

• Blood glucose rises.
• Pancreatic beta cells increase insulin secretion.
• Insulin promotes glucose uptake in skeletal muscle and adipose tissue, promotes glycogen synthesis, and suppresses liver glucose output.
• Blood glucose falls back toward its regulated range.

During fasting

• Dietary glucose disappears and insulin falls.
• Pancreatic alpha cells increase glucagon signaling.
• The liver releases glucose first through glycogenolysis and increasingly through gluconeogenesis.
• Falling insulin also permits more lipolysis and fat use.

The liver is therefore a glucose buffer: after meals it stores incoming carbon; between meals it puts glucose back into circulation.

Useful numerical anchors

These are diagnostic fasting-plasma-glucose cutoffs, not a claim that healthy glucose never moves outside them:

For people with diabetes, glucose below 70 mg/dL is commonly treated as hypoglycemia.