Glucose

Glucose is the primary fuel your body uses for energy. Every cell relies on it, and your brain is particularly dependent, consuming roughly 20% of your daily glucose supply despite making up only about 2% of your body weight. After you eat, carbohydrates are broken down into glucose, which enters the bloodstream and is shuttled into cells with the help of insulin. A fasting glucose test measures the amount of sugar in your blood after an overnight fast, giving a baseline reading of how well your body manages blood sugar overnight. It provides a snapshot of your metabolic health at that moment, whereas HbA1c gives you the longer term average over two to three months.

Mildly raised fasting glucose can be an early signal that your body is beginning to struggle with blood sugar regulation. This might progress through a stage known as impaired fasting glucose (sometimes called pre-diabetes) before reaching levels associated with type 2 diabetes. Lifestyle changes (regular physical activity, a balanced diet, maintaining a healthy weight and good sleep) can be effective at improving blood sugar control. Low fasting glucose is less common and can cause shakiness, sweating, confusion, and irritability. It may occur after prolonged fasting, intense exercise, or with certain medications.

Because glucose fluctuates throughout the day and is influenced by recent meals, stress, and activity, it is best interpreted alongside HbA1c and, where available, fasting insulin. If your glucose level is outside the expected range, your GP can arrange further testing and provide personalised guidance on management.