What is the Glucose Challenge Test?

Glucose Challenge test, abbreviated as GCT, measures your body’s response to glucose. It aims to diagnose gestational diabetes or diabetes that develops during pregnancy. It is also considered to be an effective, convenient, and affordable test for evaluating the presence of pre-diabetes or early diabetes. This test, taken at the right time, is usually beneficial in delaying or preventing the development of diabetes and its side effects.

Why is the Glucose Challenge Test Done?

The glucose challenge test analyses how the human body responds to glucose or sugar. This test is specifically advised to assess the risk of diabetes amongst people whom the doctor suspects may develop the medical condition. As it will enable the doctor to take immediate action. GCT is also recommended to individuals during a specific period of time, for instance, pregnant women.

If the results of the test are abnormal, implying that it is below or over the acceptable range, your doctor will determine the course of treatment for you. In case the results are normal, your doctor will recommend other medical tests. This is to diagnose the underlying cause of the symptoms being experienced by you.

Prerequisites for the Glucose Challenge Test

There are no preparations that need to be followed before taking the glucose challenge test. This implies that you need not fast before taking this test, unlike some other medical blood tests. However, it is best to discuss with your doctor if fasting is required and if your health condition permits to do so. Your doctor will advise you about any food-related specific dos and don’ts.

Let your doctor know the medications that you might be taking at the moment or have taken in the recent past. These medications include prescription medications, non-prescription or OTC (over-the-counter) medications, vitamins, supplements, and herbals. It also includes illicit drugs that you may be taking. This is because there are some medications that adversely affect the accuracy of the results of the GCT. Your doctor will guide you regarding the medications that you may have to stop taking for a certain time period before the test.

Understanding the Results of the Glucose Challenge Test

The glucose challenge test is measured in milligrams per decilitre (mg/dL) or millimoles per litre (mmol/L). Here are the implications of the GCT:

Normal: A blood sugar level less than 140 mg/dL (7.8 mmol/L) is considered normal.

Gestational diabetes: A blood sugar level of 140 mg/dL (7.8 mmol/L) and higher may imply the presence of gestational diabetes. However, this range differs amongst laboratories. Some labs consider 130 mg/dL as the acceptable lower limit while analysing gestational diabetes.

Your doctor will help you interpret the results and plan the next line of action.

When should the Glucose Challenge Test be Repeated?

This blood test is repeated several times within a span of 3 hours, once every 30 to 60 minutes. In case your test result indicates a strong probability of gestational diabetes, you will be recommended another test. It is called the glucose tolerance test which is done to confirm the diagnosis.

If you are under treatment, your doctor may advise you GCT at regular intervals to check the progress of the treatment. You will be asked to repeat the test to confirm whether the treatment has been successful in reducing the blood sugar level to the normal level.

Procedure for the Glucose Challenge Test

For the test, you will have to drink 148 millilitres (5 ounces) of a glucose solution. This solution comprises 50 grams of sugar. You will be asked to wait for 30 minutes to 1 hour, after which you will be offered the same glucose solution again.

About an hour later, blood will be drawn as a sample from a vein from your arm. After cleaning the area from where the blood will be taken, the technician will tie an elastic wrap around the arm. Once the vein is prominent and filled with blood, a sample will be taken using an injection. This sample will be sent to the laboratory to check your level of blood sugar.

The puncture area will be cleaned of any oozing blood and a bandage will be applied. This bandage can be removed after some time.

Glucose Challenge Test: Why and How is it Done?