Clinical Corner
Breaking down glucose, glycogen, and glucagon in diabetes
Published: Jun. 10, 2025
8 min read
The content in this article should not be taken as medical advice. Please consult with your healthcare provider regarding your individual health needs.
Every function of your body requires energy. Glucose is the primary source of energy that your body taps into because it’s fast and readily available compared to other types of energy such as fat or protein. Glucose is the energy source that fuels the immediate boost, while glycogen is one of the ways excess glucose is stored in your body. It’s important to understand the nuts and bolts of how glycogen, glucose, glucagon, and insulin work in your body to make decisions that can help you keep your glucose levels in a healthy range and avoid long-term complications from diabetes.
What is glucose?
Glucose is a simple sugar molecule (monosaccharide) that circulates in the bloodstream and provides immediate energy to your cells through a process called glycolysis, or "sugar splitting." Insulin is needed for glucose to be able to move from the bloodstream into the cells of your body and be converted to energy. If you have diabetes, your body either doesn't produce insulin (type 1) or it doesn't respond to insulin as well (type 2), so glucose gets stuck in the bloodstream and can't be used by your cells. Because of this, it’s important to monitor your glucose levels to avoid complications from hyperglycemia (high glucose) or hypoglycemia (low glucose).
Put simply, your body gets glucose from the food you eat that contains carbohydrates. Your body can also convert other forms of foods into glucose through various processes, but carbohydrates are the most direct source.
What is glycogen?
Glucose becomes glycogen through a process called glycogenesis-a set of chemical reactions using enzymes that convert it into glycogen. Glycogen is a complex carbohydrate (polysaccharide) formed by long chains of glucose linked together, stored mostly in the liver and muscles but also in the kidneys, brain, heart, fat and blood cells. Think of it as the body’s stored source of quick energy. When glucose levels drop, the body breaks down glycogen to release glucose for the energy it needs. This is called glycogenolysis. If glucose levels continue to stay low or more glucose is needed after glycogen supplies are depleted, your body will start to break down fat into energy instead, which is a much slower process.
Your glucose levels might drop for several reasons such as:
- Physical activity, such as an intense workout, or playing a sport
- Illness
- Going a long time without consuming food
It's important to note, when your body breaks down glycogen, it does not release a precise, exact amount of glucose. This is why you may see a glucose spike during a particularly strenuous exercise.
If you live with diabetes, this could potentially send your glucose levels out of range and require insulin adjustments to bring it back in range.
What is glucagon?
Glucagon is a hormone that tells the body to break down stored glycogen and release it as glucose. You can think of it as the opposite of insulin.
Glucagon is released from the pancreas and signals the liver to transform stored glycogen into glucose and release it into the bloodstream. This helps maintain a consistent supply of glucose in the body, particularly during periods of fasting or between meals.
Insulin tells your cells to absorb glucose from the bloodstream when glucose gets too high. People with diabetes using insulin are usually prescribed glucagon as part of their management routine as a protective measure against severe lows.1
Why should you know about glucose, glycogen and glucagon?
Since glucose, glycogen, and glucagon are all crucial for blood sugar regulation, people living with diabetes should know these basics about them:
- Glucose is the primary energy source for the body, so its levels must be monitored and kept in an optimal range for normal functioning and to avoid complications from high or low glucose levels.
- Glycogen offers stored energy that can be unlocked when your body has an urgent need.
- Glycogen must be replenished after it is depleted, and that happens when we eat. You should always consult your primary care doctor, endocrinologist, and/or dietitian before making any changes to your nutrition plan.
- Glycogen breakdown is activated by physical activity and fasting.
- Glucagon tells the body to break down glycogen and release glucose, so your body gets the energy it needs. It’s also an important medication to have in your diabetes toolkit.
Continuous glucose monitoring helps with the balancing act
The Dexcom G7 Continuous Glucose Monitoring (CGM) System gives you the ability to see your glucose levels in real time* and helps you manage your glucose levels more easily.
Here are two examples of how Dexcom G7 helps by serving as a compass to guide you:
- When your glucose levels are falling:
- Dexcom G7 can alert you when your glucose level is falling below your target range. When this happens, your body may try to adjust by breaking down stored glycogen. However, sometimes the glucagon response can be altered and not work fast enough. Or if you previously had a low glucose event, your glycogen stores may be depleted. Meanwhile for those who use insulin, previous doses cannot be "turned off" and will keep signaling the cells to uptake glucose, making your blood glucose levels go even lower.
- With the predictive Urgent Low Soon alert† on Dexcom G7, you can be alerted of a severe low up to 20 minutes before it happens, allowing you to make proactive decisions about how to treat or prevent hypoglycemia.
- When you’re adjusting your eating habits:
- Since your body builds up its glycogen supply through eating, there are a variety of ways of eating that can support you. Using Dexcom G7 enables you to see how different foods affect your glucose levels, helping you understand what may work best for you, your body, and your routine. Along with working with your doctor, Dexcom G7 can help you determine a precise approach.
- For example, low carb eating patterns might work well on some days when you aren’t as active. However, on days when you're more active, you might find that you don't have the energy you need.
- With Dexcom G7, you can see which types of foods and eating patterns work best for you and your specific needs, so you can manage your glucose levels more easily. It also can help you make confident decisions about lifestyle choices such as activity and meals.
Understanding glucose and glycogen can help you maximize your nutrition, optimize your daily diabetes management routine, and ensure you have the energy your body needs. Dexcom G7 is a tool that can enable you to learn more about yourself and know what is best uniquely for you as you manage your diabetes.
Get started on Dexcom G7
If you are living with diabetes and not using a CGM, we can help get you started. Click the button below to send us some basic information.
*Compatible smart devices sold separately: dexcom.com/compatibility. †Audible and visual notification of predictive alert at 55 mg/dL within 20 minutes.
1 Severe hypoglycemia (severe low blood glucose). Severe Hypoglycemia | ADA. (n.d.). https://diabetes.org/living-with-diabetes/hypoglycemia-low-bloodglucose/severe#:~:text=Glucagon%2C%20prefer
BRIEF SAFETY STATEMENT: Failure to use the Dexcom Continuous Glucose Monitoring System and its components according to the instructions for use provided with your device and available at https://www.dexcom.com/safety-information and to properly consider all indications, contraindications, warnings, precautions, and cautions in those instructions for use may result in you missing a severe hypoglycemia (low blood glucose) or hyperglycemia (high blood glucose) occurrence and/or making a treatment decision that may result in injury. If your glucose alerts and readings from the Dexcom CGM do not match symptoms, use a blood glucose meter to make diabetes treatment decisions. Seek medical advice and attention when appropriate, including for any medical emergency. Dexcom, Dexcom Clarity, Dexcom Follow, Dexcom One, Dexcom Share, and any related logos and design marks are either registered trademarks or trademarks of Dexcom, Inc. in the United States and/or other countries.