Blood glucose level (BGL) refers to the amount of glucose, a type of sugar, present in the bloodstream. Glucose serves as the body’s primary source of energy, fueling various cells and organs. It is fundamental for maintaining normal bodily functions. This essential sugar is continuously circulated through the blood to reach every cell where it is needed.
The Body’s Energy Source
Glucose is a crucial energy source derived from carbohydrates consumed in food. During digestion, carbohydrates are broken down into glucose, which is then absorbed into the bloodstream. Once in the blood, glucose is transported to cells throughout the body to produce adenosine triphosphate (ATP), the main energy currency of cells.
This energy is vital for the proper functioning of organs like the brain, muscles, and other tissues. The brain, for instance, relies on a steady supply of glucose for optimal performance, consuming a significant portion even at rest. Muscles also utilize glucose during physical activity, converting it into ATP to power contractions. Any excess glucose not immediately used for energy can be stored as glycogen in the liver and muscles.
Keeping Levels Balanced
The body maintains blood glucose levels within a narrow range through a finely tuned process known as glucose homeostasis. This balance is regulated by two key hormones produced by the pancreas: insulin and glucagon. These hormones work in opposition to ensure glucose availability while preventing levels from becoming too high or too low.
When blood glucose levels rise, typically after a meal, the pancreas releases insulin. Insulin signals cells throughout the body, particularly muscle, fat, and liver cells, to absorb glucose from the bloodstream. This process lowers blood glucose levels and allows cells to use glucose for energy or store it as glycogen.
Conversely, if blood glucose levels drop, such as between meals or during fasting, the pancreas releases glucagon. Glucagon signals the liver to convert its stored glycogen back into glucose and release it into the bloodstream. This mechanism helps to raise blood glucose levels, ensuring a continuous supply of energy for bodily functions.
Measuring Blood Glucose
Monitoring blood glucose levels provides important insights into the body’s energy management. A common method for daily measurement involves a finger-prick test using a glucometer, which provides a real-time reading. These devices require a small drop of blood placed on a disposable test strip, offering a convenient way to check levels at home.
Normal blood glucose ranges vary depending on factors like meal timing. For most healthy individuals, a fasting blood glucose level (after at least 8 hours without eating) typically falls between 72 to 99 milligrams per deciliter (mg/dL), or 4.0 to 5.4 millimoles per liter (mmol/L). Two hours after eating, blood glucose levels generally remain below 140 mg/dL (7.8 mmol/L).
Another important measure is the A1C test, also known as glycated hemoglobin. This blood test reflects average blood glucose levels over the preceding two to three months. Glucose in the bloodstream binds to hemoglobin, a protein in red blood cells; the A1C test measures the percentage of hemoglobin with glucose attached. A normal A1C level is typically below 5.7%.
When Levels Are Off
Deviations from normal blood glucose levels can occur, leading to two main states: hyperglycemia and hypoglycemia. Hyperglycemia refers to blood glucose levels that are too high. Common immediate symptoms include increased thirst, frequent urination, and feeling weak or unusually tired. These symptoms often develop slowly over days or weeks.
Conversely, hypoglycemia signifies blood glucose levels that are too low. Immediate symptoms can manifest quickly and may include shakiness, sweating, a fast heartbeat, hunger, and dizziness. If blood glucose continues to drop significantly, symptoms can progress to confusion, difficulty concentrating, or even loss of consciousness. Sustained imbalances in blood glucose, whether too high or too low, can affect overall health.