Glucose Tolerance Test In Diagnosis of Gestational Diabetes

ID-100113152Gestational diabetes is diabetes (high blood glucose level) that develop during pregnancy and usually disappear after delivery. If you have gestational diabetes, you are at greater risk of developing diabetes later in life, even if your blood sugar level comes down to normal after delivery. High blood glucose level during pregnancy can harm the fetus and baby. Hence, it is important to diagnose gestational diabetes.

For diagnosis or screening of gestational diabetes a modified glucose tolerance test is recommended by most Obstetrics associations including American Congress of obstetricians and Gynecologists. This test is done during 24th to 28th week of pregnancy, if you are not a high risk patient. Your doctor may recommend the glucose tolerance test at earlier time if you are at high risk of developing gestational diabetes (high risk women include gestational diabetes in earlier pregnancy, obesity, family history of diabetes, have medical conditions that increase risk of diabetes such as metabolic syndrome).

Glucose tolerance test for gestational diabetes:

You fast overnight (at least for eight hours without any calorie consumption, except water) and report next day to doctor’s clinic or lab.

  • A blood sample is taken after you report for fasting blood glucose level test.
  • After that you are given 100 grams of syrupy glucose to drink (8 ounce of glucose syrup containing 100 grams of glucose).
  • Blood samples are taken at one, two and three hours after consuming the 100 gram glucose syrup. After drinking glucose solution, you will have to wait in lab for taking blood samples one, two and three hours later. Once all the three blood samples are taken, you can go home.


  • At one hour, a normal blood glucose level is less than 180 mg/dl (10 mmol/L) after 100 gram glucose intake.
  • At two hours normal blood glucose level is less than 155 mg/dl (8.6 mmol/L) after 100 gram glucose intake.
  • At three hours normal blood glucose level is less than 140 mg/dl (7.8 mmol/L) after 100 gram glucose intake.
  • If your blood glucose in higher than 190 mg/dl or 10.6 mmol/L after one hour, you can be declared gestational diabetes directly, without going for two and tree hour tests.

If only one test is higher than normal then your doctor may ask you to repeat the glucose tolerance test in few weeks. If two or all the test results are higher than normal you will be diagnosed gestational diabetes. If you have gestational diabetes, it important to carefully manage blood glucose for the rest of the pregnancy and prevent complications due to diabetes during pregnancy. After delivery too, you need to take precautions to try to prevent development of diabetes later on.


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