Understanding Glucose Tolerance Test: Normal Range Results and Interpretation

Did you know the primary source of energy in your body is blood glucose? It is the main sugar found in your body and is derived from the food you consume. Basically, when you eat, your body turns food into glucose, releasing it into the blood. The rising blood glucose prompts the pancreas to release insulin, a hormone that enables glucose entry into the cells for energy production. As the glucose is absorbed into the cells, the level of glucose in blood falls.

Insufficient insulin production or usage can result in high blood glucose levels, which eventually leads to diabetes. The accumulation of glucose in the bloodstream can lead to serious health issues.

Glucose tolerance test (GTT) is a diagnostic tool used to assess how the body processes sugar and plays a vital role in managing diabetes. Glucose tolerance test helps identify prediabetes, gestational diabetes, and type 2 diabetes, enabling healthcare professionals to develop personalised treatment plans, monitor glycaemic control, and reduce the risk of diabetes-related complications. Let’s take a detailed look at blood glucose testing.

Glucose Tolerance Test: Meaning

The glucose tolerance test’s key role is to determine whether the body can store and use blood sugar normally. The test can be of two types, oral and intravenous. The oral glucose tolerance test (OGTT) is more commonly done and checks the ability of your body to process sugar.  Elevated blood sugar levels may indicate inadequate sugar absorption by cells, pointing to possible diabetes. In gestational diabetes, pregnancy hormones often lead to increased blood sugar levels, which typically normalise after childbirth.

On the other hand, the intravenous (IV) glucose tolerance test (IGTT), is infrequently employed and not used for diagnosing diabetes. In this test, glucose is administered into a vein for 3 minutes. Blood insulin levels are noted before the injection, and after 1 and 3 minutes. The time of this check may vary. This type of blood glucose testing is mainly reserved for research purposes.

For OGTT, you need to follow some guidelines that are as under:

• Ensure that you consume regular meals leading up to the test over the course of three days. 
• Abstain from eating or drinking anything for a minimum of 8 hours before the test. Eating during the test period is not allowed. 
• Consult your healthcare provider to ascertain whether any of the medications you are taking might influence the test outcomes. 
• Your doctor will refrain from doing the test if you are unwell, especially, if you have an infection. 

The process of OGTT is as follows: A fasting blood sugar (FBS) test will be done before the test starts. Following this, you will be instructed to drink a liquid containing a specified amount of glucose (glucose challenge test), typically about 75 grams. Subsequently, blood samples will be taken at intervals of 30 to 60 minutes after consuming the glucose solution. The entire test procedure might extend up to 3 hours. 

OGTT test results do not determine if the test was properly prepared and administered. It evaluates glucose tolerance during the test and provides a qualitative indication of average blood glucose and HbA1c (normal, high, very high). It also cannot distinguish between type 1 and type 2 diabetes or predict the response to hypoglycaemic therapy or the risk of diabetes complications. 

Benefits of Glucose Tolerance Testing

Regular glucose tolerance tests can be quite vital to managing your diabetes. Some benefits of blood glucose testing include:

• The OGTT is a crucial technique for screening diabetes. This can help identify diabetes at an earlier stage and allow for timely treatment. 
• The glucose tolerance test also plays a very important role in gestational diabetes. Early detection can help prevent complications like pre-eclampsia (high blood pressure during pregnancy). 
• The OGTT identifies problems in how the body deals with glucose after a meal, generally before the issues can be identified on fasting blood glucose level tests. 
• Test results can indicate normal blood sugar, impaired glucose tolerance or pre-diabetes, and diabetes.

Interpreting Glucose Tolerance Test Results

Glucose tolerance test results may vary depending on the labs and the samples used. Moreover, certain medications, illnesses, recent trauma or surgery, and carbohydrate intake during the test can hinder test results. So, remember to let your doctor know about the medications you are taking. Let’s take a look at the values of glucose tolerance test results. 

Normal glucose tolerance test results indicate no diabetes. The glucose tolerance test normal range for 75-gram OGTT, which is used to test for type 2 diabetes in non-pregnant individuals, is as follows:

• Fasting: 60 to 100 mg/dL (3.3 to 5.5 mmol/L)
• After 1 hour: Less than 200 mg/dL (11.10 mmol/L)
• After 2 hours: Less than 140 mg/dL (7.8 mmol/L). The result of this test is crucial for diagnosing diabetes. 

OGTT test results with higher than glucose tolerance test normal values may indicate pre-diabetes or diabetes:

• A 2-hour test result of between 140 to 199 mg/dL (7.8 to 11.10 mmol/L) is referred to as impaired glucose tolerance or pre-diabetes and indicates an increased risk of developing diabetes in the future.
• A glucose level of 200 mg/dL (11.1 mmol/L) or higher at any point in the test indicates diabetes.

Your healthcare provider can help resolve any doubts you might have regarding your glucose tolerance test results. They can prescribe you the appropriate diet, medications, and lifestyle changes if necessary.

Book Glucose Tolerance Test Online at Home With Orange Health Labs

With the various developments in the lab testing universe, it is now easy to book tests like glucose tolerance tests easily at home. Here are a few quick steps you can follow to get a test for glucose tolerance: 

• Visit the “Orange Health Lab” site.
• You can select your location.
• Next, click on “Lab Tests.”
• You can then go ahead and choose from the glucose tolerance test packages available based on the recommendation of your doctor. 

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Glucose tolerance tests are like undercover detective