What Does Glucose Do?

Medically Reviewed By William C. Lloyd III, MD, FACS
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Young diabetic woman having breakfast at home

Glucose is fuel for the human body.

When we eat food, the body breaks that food down into simpler substances that your cells, tissues, and organs use in the chemical processes that support life. The process of digestion helps turn complex carbohydrates (such as bread, pasta, rice, potatoes, and other vegetables) into glucose. Fruits and dairy products also contain natural sugars that the body converts to glucose, and the body can use fat and protein to make glucose as well.

Inside the body, glucose is known as “blood sugar” because it is transported via the blood to all the cells of the body. Normal fasting blood sugar ranges between 70 to 99 mg/dL; two hours after eating, a normal blood sugar level is less than 140 mg/dL. Higher-than-normal blood sugar levels indicate a problem with the body’s functioning. (Infections and diabetes can both cause high blood glucose levels.)

How Glucose Works

Remember: glucose functions as fuel for the human body. It is transported throughout the body by the blood, so you can think of the circulatory system (blood vessels + blood) as a fuel pipeline. The pipeline carries the fuel (glucose), but the glucose needs help to get into the cells of the body. Just as fuel can’t exit the pipeline unless someone opens a valve, glucose can’t get into the cell without the help of insulin, a hormone that tells the cells to let in glucose.

A healthy pancreas, an organ located behind the human stomach, secretes the hormone insulin when it detects a rise in blood sugar levels (typically, after eating). The insulin “opens the valve,” so to speak, allowing glucose to move from the blood into the cells of the body. The cells can immediately use the glucose for energy or store it for later use.

Glucose and Diabetes

When a person has diabetes, glucose (blood sugar) levels remain higher than they should because glucose can’t effectively get into the cells of the body, which means the body has less access to the fuel it needs to function well. Instead, the “fuel”—glucose—is stuck in the “pipeline,” or circulatory system.

Without sufficient access to glucose, the body burns fat instead for energy. But just as using the wrong type of fuel in your car (diesel, say, instead of gasoline) can damage your vehicle, burning fat for energy over an extended period of time can cause a potentially life-threatening condition called diabetic ketoacidosis. Insulin is necessary to treat diabetic ketoacidosis.

Your body can’t function well without glucose (and insulin). Anything that interferes with your blood glucose and insulin levels can negatively affect your health. Your healthcare provider can help you better understand how glucose functions in the body, and work with you to address any issues with how your body processes glucose.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jun 27
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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