The human body needs energy to work, and most of that energy comes from glucose. Glucose is a type of sugar that powers your brain, muscles, and organs.
When you eat carbohydrates, your body breaks them down into glucose and uses what it needs right away. The extra glucose gets stored as glycogen in your liver and muscles for later use. But how does glycogen turn into glucose when your body needs more energy?
Understanding this process helps you see how your body keeps energy levels stable between meals, during exercise, or at night when you’re asleep.
What Is Glycogen?
Glycogen is the storage form of glucose. It’s a large molecule made up of many glucose units linked together. Most glycogen is stored in your liver and skeletal muscles.
The liver acts like a glucose bank; it releases glucose into your bloodstream when your body needs it. Your muscles, on the other hand, store glycogen for their own use during movement or physical activity.
According to research from the National Institutes of Health (NIH), the human body can store about 100 grams of glycogen in the liver and around 400 grams in the muscles, depending on diet, body size, and fitness level.
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How the Body Uses Glycogen
When your body needs energy, such as between meals, during exercise, or when blood sugar drops, it signals certain hormones to act.
The main hormones involved are glucagon and epinephrine (adrenaline). These hormones send a message to your liver and muscles to start breaking down glycogen into glucose.
This process is known as glycogenolysis. It’s how glycogen turns into glucose so that your body can keep functioning, even when you haven’t eaten recently.
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Step-by-Step: How Does Glycogen Turn Into Glucose
To understand the full picture, here’s a simple step-by-step breakdown of the process:
- Hormone signal: When blood sugar drops, the pancreas releases glucagon. During exercise or stress, the adrenal glands release epinephrine.
- Enzyme activation: These hormones activate enzymes such as glycogen phosphorylase, which begins to break down glycogen.
- Glucose release: Glycogen phosphorylase removes one glucose molecule at a time from the glycogen chain, forming glucose-1-phosphate.
- Conversion: Glucose-1-phosphate changes into glucose-6-phosphate through another enzyme called phosphoglucomutase.
- Final step: In the liver, glucose-6-phosphate is converted into free glucose by the enzyme glucose-6-phosphatase. That glucose then enters the bloodstream to raise blood sugar levels and supply energy to cells.
In muscles, the process stops at glucose-6-phosphate because muscle cells don’t have the enzyme glucose-6-phosphatase. Instead, they use that glucose-6-phosphate directly for energy during movement or physical activity.
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The Role of the Liver and Muscles
Both the liver and muscles store glycogen, but they serve different purposes. The liver maintains steady blood glucose levels for the entire body.
For example, when you’re sleeping or between meals, liver glycogen breaks down into glucose and keeps your brain and organs working properly.
Your muscles, however, use glycogen locally. During exercise, muscle glycogen quickly breaks down into glucose to provide immediate energy.
According to the American Physiological Society, during intense exercise, muscle glycogen can fuel up to 80% of your energy needs.
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How Long Does Glycogen Last?
The amount of time glycogen can sustain you depends on activity and diet. During rest, liver glycogen can keep blood sugar normal for about 12 to 18 hours. During heavy exercise, muscle glycogen can run out in less than two hours.
Endurance athletes often practice something called “carb loading” to boost glycogen stores before events. Research from the American College of Sports Medicine (ACSM) shows that increasing carbohydrate intake before endurance exercise can double glycogen stores and improve performance.
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Why Glycogen Breakdown Is Important
The process of how glycogen turns into glucose is essential for maintaining steady energy. Without it, your blood sugar would drop too low, leading to symptoms like dizziness, fatigue, confusion, or even fainting.
This system also protects your muscles and brain. Since the brain cannot store glycogen, it relies on the liver to release glucose into the blood. Muscles, in turn, depend on their own glycogen to keep moving during workouts or physical tasks.
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Factors That Affect Glycogen Breakdown
Several factors can change how efficiently your body converts glycogen into glucose:
- Diet: Low-carb diets can lower glycogen stores.
- Exercise intensity: High-intensity workouts use glycogen faster.
- Hormonal balance: Issues with insulin or glucagon can slow the process.
- Health conditions: Liver diseases or metabolic disorders may affect glycogen storage and release.
- Recovery time: Proper rest and refueling help replenish glycogen after exercise.
According to the Journal of Applied Physiology, eating a balanced meal with carbohydrates and protein within two hours after exercise helps restore glycogen faster.
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Maintaining Healthy Glycogen Levels
Keeping glycogen stores at a healthy level supports steady energy throughout the day. Here are a few ways to maintain balance:
- Eat balanced meals: Include healthy carbs like whole grains, fruits, and vegetables.
- Stay active: Regular exercise helps your body use and store glycogen more efficiently.
- Refuel after workouts: Replenish glycogen by eating carbs and protein after exercise.
- Get enough sleep: Rest supports hormone balance and energy recovery.
- Avoid skipping meals: Long gaps between meals can cause low blood sugar and stress your glycogen reserves.
A Word from GetMe Treated
Understanding how does glycogen turn into glucose helps you see how your body manages energy between meals and during activity.
Glycogen serves as a backup system, ready to keep your body running when blood sugar drops. The liver provides glucose for the whole body, and muscles use their own stores for strength and endurance.
Research from the National Institutes of Health (NIH) and the American Diabetes Association (ADA) supports the importance of this process for maintaining energy and preventing low blood sugar.
By eating right, staying active, and giving your body time to recover, you can keep your glycogen and glucose systems working smoothly.
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FAQs About How Does Glycogen Turn Into Glucose
What triggers glycogen to turn into glucose?
Low blood sugar or physical activity triggers hormones like glucagon and epinephrine, which start the glycogen breakdown process.
Where is glycogen stored in the body?
It’s mainly stored in the liver and muscles.
How long can glycogen stores last?
Liver glycogen can last about 12–18 hours at rest, while muscle glycogen can deplete in a few hours of intense exercise.
Does eating sugar increase glycogen?
Yes, eating carbohydrates increases glycogen stores once your body processes the glucose and stores the excess.
Can you run out of glycogen completely?
Yes. When glycogen runs out, you may feel tired, weak, or experience “hitting the wall” during long workouts.
What foods help restore glycogen?
Foods rich in carbohydrates, like rice, potatoes, oats, fruits, and whole grains, help restore glycogen levels.