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Fasting Blood Glucose

Diabetes Screening

5 minutesBlood draw

A blood test that measures blood sugar levels after an overnight fast.

Duration
5 minutes
Sample Type
Blood draw ()
Results Timeline
1 business day
Requires 8-12 hours of fasting

How to Prepare

Follow these instructions to ensure accurate test results

8-12 hours before
No food or drinks except water
Evening before
Eat dinner at normal time, then begin fasting
Things to Avoid
  • •All food and beverages except water
  • •Coffee and tea (even black)
  • •Chewing gum and mints

Day of Your Test

  • Schedule for early morning to minimize fasting time
  • Water is allowed and encouraged
  • Check with doctor about taking medications
  • Bring a snack for after the test

What This Measures

To screen for diabetes and prediabetes, and monitor blood sugar control.

  • •Blood sugar (glucose) levels after fasting
  • •How well your body regulates blood sugar overnight
  • •Risk of developing diabetes

Why This Test Matters

Fasting glucose is a key indicator for diabetes risk. Early detection allows for lifestyle changes and treatment that can prevent or delay diabetes and its complications.

Normal Ranges

Normal
Healthy blood sugar
Below 100 mg/dL
Prediabetes
Impaired fasting glucose
100-125 mg/dL
Diabetes
Requires confirmation
126 mg/dL or higher

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

After the Test

  • Eat normally after the test
  • Resume all regular activities
  • Take any medications you held for the test

Understanding Results

If High

Elevated fasting glucose may indicate prediabetes or diabetes. Your doctor may recommend additional tests like A1C or glucose tolerance test.

If Low

Low fasting glucose (hypoglycemia) is uncommon but may indicate other conditions or medication effects.

Good to Know

  • Stress and illness can temporarily raise blood sugar
  • Results should be confirmed with a second test on a different day
  • Time of day affects glucose levels - morning tests are most accurate

Follow Up

  • •If prediabetic: lifestyle modifications and retest in 3-6 months
  • •If diabetic: additional testing and treatment planning
  • •For healthy results: retest every 3 years or as recommended

Source: Test preparation information is based on standard clinical guidelines and laboratory best practices. This information is provided for reference purposes only and should not replace professional medical advice, diagnosis, or treatment. Always follow the specific instructions provided by your healthcare provider or laboratory.