Fasting Blood Sugar

Also known as: FBS, Fasting Glucose, FPG

Diabetes & Hormones Blood (after 8–12 hours fasting)
Patient Friendly Summary

This is your sugar level on an empty stomach. One high reading does not equal diabetes — stress, illness, or improper fasting can affect it. Your doctor will confirm before labelling anything.

What this test means

Fasting sugar shows your baseline glucose level without the effect of recent meals. It is a core test for diagnosing and monitoring diabetes.

Why it is done

It is done for diabetes screening, monitoring known diabetes, and evaluating symptoms like excessive thirst, urination, or unexplained weight loss.

Understanding your value

If your value is high

Values of 126 mg/dL or more on repeat testing can suggest diabetes; 100–125 mg/dL may suggest prediabetes.

If your value is low

Low values can be seen with skipped meals, excess diabetes medicine, or other causes, and may cause shakiness, sweating, or giddiness.

About the normal range

A common normal fasting range is 70–99 mg/dL. Diagnosis is never made on one value alone — doctors confirm with repeat tests or HbA1c.

When to consult a doctor

Consult your doctor if your fasting sugar is repeatedly above 100 mg/dL, or promptly if you have symptoms of very high or very low sugar.

Frequently Asked Questions

It is done for diabetes screening, monitoring known diabetes, and evaluating symptoms like excessive thirst, urination, or unexplained weight loss. Your doctor will decide if this test is right for your situation.

Values of 126 mg/dL or more on repeat testing can suggest diabetes; 100–125 mg/dL may suggest prediabetes. This needs clinical correlation — always discuss your report with your doctor.

Low values can be seen with skipped meals, excess diabetes medicine, or other causes, and may cause shakiness, sweating, or giddiness. This needs clinical correlation — always discuss your report with your doctor.

A single value rarely tells the whole story. Results need to be read together with your symptoms, history, and other tests. Please consult your doctor for a proper interpretation.

Quick Facts

  • TestFasting Blood Sugar
  • Short formsFBS, Fasting Glucose, FPG
  • Sample typeBlood (after 8–12 hours fasting)
  • CategoryDiabetes & Hormones

Related Terms

Diabetes Control Borderline High Low

Specialists

Endocrinology & Diabetology General Medicine

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Disclaimer: This information is for patient education only and does not replace medical advice, diagnosis, or treatment. Always consult a qualified doctor.