Fasting Blood Sugar

What is Fasting Blood Sugar?

Fasting blood sugar (FBS) is a simple blood test that measures the amount of glucose (sugar) in your blood after you have not eaten for at least 8 hours. It helps doctors understand how well your body regulates blood sugar.

Key Parameter

Why is it done?

• Routine health check‑ups
• Evaluation of symptoms such as excessive thirst, frequent urination, or unexplained weight loss
• Monitoring of people with diabetes or at risk of diabetes
• Screening for gestational diabetes during pregnancy

Early Detection

FBS can help identify signs of prediabetes and type 2 diabetes, but it does not diagnose on its own. A doctor interprets the result together with symptoms, medical history, and other tests.

What does an abnormal result mean?

• High: May indicate impaired glucose tolerance, prediabetes, or diabetes. Factors such as recent stress, illness, or certain medications can also raise levels.
• Low: Can occur in fasting hypoglycemia, certain endocrine disorders, or after excessive alcohol intake. Many factors, including hydration and medication timing, can influence results.

Who should get this test?

• Adults over 45 years old
• Individuals with a family history of diabetes
• People with obesity, high blood pressure, or abnormal cholesterol
• Pregnant women after 20 weeks of gestation
• Anyone experiencing symptoms of high or low blood sugar

Short summary: Fasting blood sugar measures glucose after an overnight fast, helping detect or monitor diabetes and related conditions.

Preparation

• Fasting required: Yes, fast for at least 8 hours (no food or drinks except water).
• If combined with other fasting tests: Follow the longest fasting period required among the tests.
• Procedure: A healthcare professional will clean the arm with an antiseptic, insert a needle into a vein, and collect about 5 mL of blood. The whole process takes 5–10 minutes.
• What to expect: A brief pinch and a small amount of blood drawn; you may feel a slight sting.
• Precautions: Stay hydrated before the test, avoid alcohol and strenuous exercise 24 hours prior, and take any regular medications as prescribed unless your doctor advises otherwise.
• Final note: Confirm specific preparation instructions with your doctor or the lab. This information is general educational guidance and not a substitute for professional medical advice.