How Does the Liver Control Glucose in the Blood?

Your body needs a constant supply of glucose, or sugar, for cells to have energy, so it requires a readily available reservoir to keep blood glucose in balance. One of the liver’s main roles in the body is controlling the amount of glucose circulating in the blood. By storing excess glucose as glycogen and creating new glucose from proteins and fat byproducts, the liver is able to maintain balanced glucose levels in your body at all times.

Formation of Glycogen

When you eat carbohydrates, the body releases glucose into the bloodstream immediately, triggering the production of insulin. The body cannot be in a state of constant consumption, so when insulin levels are high enough, the body links long chains of glucose together into a compound called glycogen, which is then stored in the liver and the muscles. The liver uses this stored glucose energy as its main reservoir for releasing glucose into the bloodstream when levels drop.

Breakdown of Glycogen

Blood glucose levels drop when you're not eating, such as during sleep or between meals. This low blood sugar signals the liver to produce glucose and release it back into the bloodstream. The liver favors glycogen as its primary source since it is efficiently broken down into glucose in a process known as glycogenolysis. In this process, the liver breaks the bonds that hold glucose molecules together as glycogen, degrading most but not all of the glycogen molecule.

Effects of Insulin Resistance

When your body is chronically subjected to high levels of blood sugar and insulin, such as after you've eaten an excessive amount of foods high in sugar, it develops a resistance to the hormone, and the liver cannot respond properly, eventually leading to type-2 diabetes if the resistance is not controlled. According to a study published in July 2005 in “Clinical Diabetes,” individuals with insulin resistance demonstrate more abnormalities in liver function tests. When insulin cannot properly signal to the liver, the liver produces more free fatty acids, changing the organ’s composition and potentially leading to additional health complications.

Liver Function in Low-Glycogen Conditions

When levels of glycogen in the liver are very low, such as when you are fasting or on a low-carbohydrate diet, the liver uses alternative sources to produce and release more glucose into the bloodstream. Through a process called gluconeogenesis, the liver can create glucose from amino acids, the building blocks of protein and fat byproducts. Low glycogen levels also trigger a process called ketogenesis, in which the liver uses fats to create ketones. Ketones can then be burned as fuel for muscles and organs.