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Blood Sugar Fasting & Post Glucose

About the test
What is this test done for?
Blood sugar fasting and post glucose, also known as glucose tolerance test, a routine blood test that measures the amount of glucose levels in the blood. It helps in screening for diabetes.
Why is it Done?
This is a routine screening blood test for diabetes.It helps in
  • Diagnosing diabetes
  • Diagnosing pre-diabetes as well as gestational diabetes
  • Monitoring the therapy for diabetes
  • Determining whether a patient has developed insulin resistance
  • As a part of pre-surgery profile
  • As a routine test for patients above 40 years of age
When should it be performed?
This test is performed
  • If a patient has symptoms of diabetes
    • Increased frequency of urination (especially at night)
    • Increased thirst
    • Increased appetite
    • Giddiness (frequent episodes)
    • Extreme fatigue
    • Delay in wound healing
    • Pus formation at the site of wounds
    • Frequent and repeated infections
  • If a woman is pregnant and is complaining of excess hunger or thirst or excessive weight gain in 2nd and 3rd trimester, this test is conducted to rule out gestational diabetes
  • If a patient already has diabetes, it helps in monitoring the therapy
  • As a routine test, if a patient has a strong family history of diabetes or impaired glucose tolerance
  • If a female patient has polycystic ovarian disease
How is it done
A blood sample will be collected from a vein in your arm. The test requires 12 hours of fasting before conducting the test. After collecting blood for fasting sugar, you will be given 75 grams of glucose dissolved in water and again blood is collected after 2 hours of taking the solution.

The test result is normal, if blood sugar fasting is 70-110 mg/dL and blood sugar post glucose is 110-140 mg/dL. It means

  • No diabetes
  • Well controlled diabetes

The test results are high, if blood sugar fasting is >110 mg/dL and blood sugar post glucose is >140 mg/dL. It means

  • Patient has diabetes
  • Blood is collected before scheduled time
  • Poorly controlled diabetes
  • Impaired glucose tolerance
  • Insulin resistance
  • Pre-diabetic
  • Gestational glucose tolerance

Test results are low, if blood sugar fasting is <70 mg/dL and blood sugar post glucose is <110 mg/dL. It means

  • Hypoglycemia
  • Prolonged fasting or blood is collected later than scheduled time
  • Excessive dose of insulin or diabetic medicines
Other Tests
  • Glycosylate hemoglobin (HbA1c)
    • It is a blood test carried out to evaluate the amount of glycosylated hemoglobin levels
    • High level of HbA1c indicate prolonged hyperglycemia
  • Blood insulin level (Fasting and Post lunch)
    • It is a specialized blood test that evaluates the amount of insulin present in the blood
    • It helps in differentiating between type 1 & type 2 diabetes
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