GLUCOSE, FASTING (F)

The fasting blood glucose test measures the amount of sugar (glucose) in your blood after an overnight fast — usually the first sample of the morning, before you eat or drink anything except water. It is one of the most commonly ordered blood tests in the world and the standard starting point for checking how your body handles sugar.

Glucose is the body's main fuel, and its blood level is tightly controlled by insulin. When that control slips — as in diabetes or prediabetes — fasting glucose rises. Because every sample is taken in the same standardised fasting state, the result gives your doctor a clean baseline to compare against, which is exactly why the overnight fast is mandatory and not optional.

When do doctors advise this test?

• Routine preventive health checkups and diabetes screening
• Symptoms that suggest high blood sugar — increased thirst, frequent urination, unexplained tiredness or slow-healing wounds
• Monitoring known diabetes, to see whether medicines, diet and exercise are keeping sugar in control
• Pregnancy checkups, where doctors watch sugar levels closely
• Before surgery, or when starting medicines that can affect blood sugar

Preparation & the sample

Overnight fasting is mandatory — usually 8 to 12 hours without food before the sample. Plain water is generally allowed and actually helps, since dehydration makes the blood draw harder; but tea, coffee, milk, juice or even chewing gum will break the fast. Morning collection is preferred. If you take diabetes medicines, do not stop or skip them on your own — ask your doctor, and mention it to the booking team on +91 9451155402. The sample is drawn into a special grey-top fluoride tube that keeps the glucose stable until testing.

This information is educational and general. Your doctor's advice for your specific situation always comes first.