Fasting Blood Sugar (FBS)
Sample Type
Blood
Tube Type
Fluoride Tube
Fasting Required
8 to 12 hours
Lab
Serum
Overview
The Fasting Blood Sugar (FBS) test measures the level of glucose (sugar) in your blood after you have not eaten for at least 8 hours. It is primarily used to screen for or monitor:
Diabetes Mellitus
Prediabetes
Hypoglycemia (low blood sugar)
Glucose is the body’s main source of energy, and maintaining normal glucose levels is vital for metabolic health. Abnormal levels can indicate problems with insulin production or action.
Test Result Interpretation
FBS Level | Glucose Range (mg/dL) | Interpretation | Possible Indications |
|---|---|---|---|
Normal | 70 – 99 mg/dL | Normal fasting glucose level | Normal metabolism |
Prediabetes (Impaired Fasting Glucose) | 100 – 125 mg/dL | Borderline glucose intolerance | Risk of developing Type 2 Diabetes |
Diabetes Mellitus | ≥ 126 mg/dL (on 2 separate tests) | High fasting glucose level | Indicates Type 1 or Type 2 Diabetes |
Hypoglycemia | < 70 mg/dL | Abnormally low blood sugar | Insulin overdose, fasting, hormone disorders |
Risk Assessment
FBS should be conducted after 8–12 hours of fasting (water is allowed).
A single abnormal reading is not enough for a diabetes diagnosis; confirmation with a repeat test or Oral Glucose Tolerance Test (OGTT) is recommended.
Certain medications, stress, and illnesses may affect glucose levels.