14.6 Blood Glucose Control

2026 📋 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Explain why it is important to control blood glucose concentration
  2. Describe how the liver and pancreas work together to control blood glucose, including the roles of the hormones insulin and glucagon
  3. Describe the signs of Type 1 diabetes and how it is treated

📖 Main Content

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1. Why Do We Need to Control Blood Glucose?

Glucose is a type of sugar. It is the main source of energy for all the cells in your body. Your blood carries glucose to every cell so that cells can use it for respiration (the process that releases energy).

It is very important that the amount of glucose in your blood — called the blood glucose concentration — stays within a safe, normal range at all times. Here is why:

  • Too much glucose in the blood is dangerous. It can damage blood vessels and organs over time. The kidneys may struggle to keep glucose out of the urine.
  • Too little glucose in the blood is also dangerous. Your brain depends almost entirely on glucose for energy. If blood glucose falls too low, brain cells cannot function properly. This can cause dizziness, confusion, unconsciousness, and even death.

Because glucose levels can rise and fall throughout the day (for example, after eating a meal or doing exercise), the body needs a system to constantly monitor and adjust blood glucose. This is an example of homeostasis — keeping conditions inside the body stable and balanced.

2. How Is Blood Glucose Controlled?

Two organs work as a team to keep blood glucose at the right level:

  • The pancreas — detects changes in blood glucose and releases hormones in response
  • The liver — receives the hormones and responds by storing or releasing glucose

🔑 What Is a Hormone?

A hormone is a chemical messenger made in one part of the body and carried in the blood to another part of the body, where it has an effect. The two key hormones in blood glucose control are insulin and glucagon, both made in the pancreas.

2a. When Blood Glucose Is Too High (e.g. After Eating)

When you eat a meal containing carbohydrates (such as bread, rice, or pasta), your digestive system breaks them down into glucose. This glucose is absorbed from the small intestine into the blood, causing blood glucose to rise.

Here is what happens step by step:

  1. The pancreas detects that blood glucose concentration has risen above the normal level.
  2. The pancreas releases a hormone called insulin into the blood.
  3. Insulin travels in the blood to the liver.
  4. Insulin causes the liver to convert excess glucose into a storage carbohydrate called glycogen (think of glycogen as a "storage form" of glucose, like packing leftover food into a container to use later).
  5. As glucose is removed from the blood and stored as glycogen, blood glucose concentration falls back to normal.

💡 Remember: Insulin lowers blood glucose. Think: Insulin → blood glucose goes In (into storage).

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