Glucose

What Is Glucose?

Glucose is a simple sugar (monosaccharide) and the primary source of energy for the human body. It is the most abundant carbohydrate in nature and serves as the universal fuel for cells. When you consume carbohydrates — whether from bread, fruit, or vegetables — your digestive system breaks them down into glucose, which then enters the bloodstream.

Blood glucose concentration is measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). A fasting blood glucose level between 70 and 99 mg/dL is considered normal for most adults.

How the Body Uses Glucose

Once glucose enters the bloodstream, the pancreas releases insulin, a hormone that signals cells to absorb glucose for energy or storage. Cells can use glucose immediately through a process called glycolysis, or store it as glycogen in the liver and muscles for later use. When glycogen stores are full, excess glucose is converted to fat.

The brain relies almost exclusively on glucose as its energy source under normal conditions, consuming approximately 120 grams per day. This makes maintaining stable blood glucose levels critical for cognitive function and overall health.

Glucose in Food and Nutrition Labels

Glucose occurs naturally in fruits, vegetables, and honey. On nutrition labels, it may appear under "Total Sugars" or listed as dextrose (its common food industry name). The glycemic index (GI) of pure glucose is set at 100, making it the reference point against which all other carbohydrates are measured.

• Glycemic Index: 100 (reference standard)
• Caloric value: 4 kcal per gram
• Chemical formula: C₆H₁₂O₆

People managing diabetes or insulin resistance must monitor glucose intake carefully, as impaired glucose metabolism underlies both Type 1 and Type 2 diabetes.