Blood Glucose – Fasting (FBS)
What Is This Test?
The Fasting Blood Sugar (FBS) test, also known as Fasting Blood Glucose (FBG) or Fasting Plasma Glucose (FPG), measures the level of glucose (sugar) in your blood after fasting for at least 8–12 hours.
Glucose is the body's primary source of energy and is regulated by the hormone insulin, which is produced by the pancreas. The FBS test helps determine how effectively your body maintains normal blood sugar levels during fasting.
It is one of the most commonly used tests to screen for diabetes, diagnose prediabetes and diabetes, and monitor blood sugar control in people with diabetes.
Why this test is performed?
Doctors may recommend the FBS test to:
- Screen for diabetes mellitus
- Diagnose prediabetes
- Diagnose Type 1 or Type 2 diabetes
- Monitor diabetes treatment
- Evaluate blood sugar control
- Assess insulin function
- Screen individuals at high risk of diabetes
- Investigate symptoms of high or low blood sugar
- Monitor people with metabolic syndrome
- Evaluate blood glucose during routine health check-ups
Test Preparation
Fast for 8–12 hours before the blood sample is collected.
During fasting, do not eat or drink anything except plain water.
Avoid tea, coffee, milk, fruit juice, chewing gum, or sugary drinks during the fasting period.
Continue medications only if advised by your healthcare provider.
Avoid alcohol for 24 hours before the test.
Avoid strenuous exercise before the test, as it may temporarily affect blood sugar levels.
Inform your healthcare provider about all medications, as some medicines (such as corticosteroids or certain diuretics) can influence glucose levels.
Medical disclaimer
This article is for general information and education only. It is not medical advice, does not create a doctor–patient relationship, and is not a substitute for consultation with a qualified doctor who has assessed your individual situation. Never delay seeking medical advice because of something you have read here.
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