Glucose Tolerance Test, 2 Specimens (75g)

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: Glucose Tolerance Test 2 Specimens 75g

2 Hour Specimen

Fasting Specimen

*Important Information on Lab Test Processing Times: Ulta Lab Tests is committed to informing you about the processing times for your lab tests processed through Quest Diagnostics. Please note that the estimated processing time for each test, indicated in business days, is based on data from the past 30 days across the 13 Quest Diagnostics laboratories for each test. These estimates are intended to serve as a guide and are not guarantees. Factors such as laboratory workload, weather conditions, holidays, and the need for additional testing or maintenance can influence actual processing times. We aim to offer estimates to help you plan accordingly. Please understand that these times may vary, and processing times are not guaranteed. Thank you for choosing Ulta Lab Tests for your laboratory needs.

The Glucose Tolerance Test, 2 Specimens (75g) test contains 1 test with 2 biomarkers.

Brief Description: The Glucose Tolerance Test, 2 Specimens, is a specialized diagnostic tool that provides valuable insights into an individual's ability to regulate blood sugar levels over a specific period. This test involves multiple blood samples taken before and after consuming a glucose-rich solution. It is a critical assessment for diagnosing conditions like diabetes and evaluating the body's response to glucose.

Also Known As: Fasting Blood Glucose Test, FBG Test, Blood Sugar Test, Fasting Blood Sugar Test, FBS Test, Fasting Glucose Test, FG Test, Glucose Tolerance Test, GTT Test, Glucose 2 Specimen Test, Glucose 1 Hour Test, Glucose half hour Test, 2 Specimen Glucose Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Fasting required

When is a 2 Specimen Glucose Tolerance test ordered?

Diabetes screening is recommended by several health groups, including the American Diabetes Association and the United States Preventive Services Task Force, when a person is 45 years old or has risk factors.

The ADA recommends retesting within three years if the screening test result is within normal limits, but the USPSTF recommends testing once a year. Annual testing may be used to monitor people with prediabetes.

When someone exhibits signs and symptoms of high blood glucose, a blood glucose test may be conducted.

Diabetics are frequently asked to self-check their glucose levels multiple times a day in order to monitor glucose levels and choose treatment alternatives as suggested by their doctor. Blood glucose levels may be ordered on a regular basis, along with other tests such as A1c, to track glucose control over time.

Unless they show early symptoms or have had gestational diabetes in a prior pregnancy, pregnant women are routinely screened for gestational diabetes between the 24th and 28th week of pregnancy. If a woman is at risk of type 2 diabetes, she may be tested early in her pregnancy, according to the American Diabetes Association. When a woman has type 1, type 2, or gestational diabetes, her health care provider will normally order glucose levels to monitor her condition throughout the duration of her pregnancy and after delivery.

What does a 2 Specimen Glucose Tolerance blood test check for?

A Glucose Tolerance test measures glucose levels in your blood over a period of time through multiple specimen. Glucose is the major energy source for the body's cells and the brain and nervous system's only source of energy. A consistent supply must be provided, and a somewhat constant level of glucose in the blood must be maintained. The glucose level in the blood can be measured using a variety of methods. 

Fruits, vegetables, breads, and other carbohydrate-rich foods are broken down into glucose during digestion, which is absorbed by the small intestine and circulated throughout the body. Insulin, a hormone generated by the pancreas, is required for the use of glucose for energy production. Insulin promotes glucose transport into cells and instructs the liver to store surplus energy as glycogen for short-term storage or triglycerides in adipose cells.

Normally, blood glucose rises slightly after you eat or drink, and the pancreas responds by releasing insulin into the blood, the amount of which is proportional to the size and substance of the meal. The level of glucose in the blood declines as glucose enters the cells and is digested, and the pancreas responds by delaying, then ceasing the secretion of insulin.

When blood glucose levels fall too low, such as between meals or after a strong activity, glucagon is released, which causes the liver to convert some glycogen back into glucose, so boosting blood glucose levels. The level of glucose in the blood remains pretty steady if the glucose/insulin feedback loop is working appropriately. When the balance is upset and the blood glucose level rises, the body strives to restore it by boosting insulin production and removing excess glucose through the urine.

Several diseases can cause the equilibrium between glucose and pancreatic hormones to be disrupted, resulting in high or low blood glucose. Diabetes is the most common cause. Diabetes is a collection of illnesses characterized by inadequate insulin production and/or insulin resistance. Untreated diabetes impairs a person's ability to digest and utilize glucose normally. Type 1 diabetes is diagnosed when the body is unable to produce any or enough insulin. People with prediabetes or type 2 diabetes are insulin resistant and may or may not be able to produce enough of the hormone.

Organ failure, brain damage, coma, and, in extreme situations, death can result from severe, sudden fluctuations in blood glucose, either high or low. Chronically high blood glucose levels can harm body organs like the kidneys, eyes, heart, blood vessels, and nerves over time. Hypoglycemia can harm the brain and nerves over time.

Gestational diabetes, or hyperglycemia that exclusively arises during pregnancy, can affect some women. If left untreated, this can result in large babies with low glucose levels being born to these mothers. Women with gestational diabetes may or may not acquire diabetes later in life.

Lab tests often ordered with a 2 Specimen Glucose Tolerance test:

When this test is ordered, it's often part of a broader evaluation of metabolic health and diabetes risk. Here are some tests commonly ordered alongside it:

  1. Hemoglobin A1c (HbA1c):

    • Purpose: To measure the average blood glucose levels over the past two to three months.
    • Why Is It Ordered: To provide an overview of long-term glucose control, which is useful in diagnosing diabetes and in monitoring the treatment of diabetes.
  2. Fasting Insulin Level:

    • Purpose: To measure the amount of insulin in the blood after fasting.
    • Why Is It Ordered: To evaluate insulin production and insulin resistance. Elevated fasting insulin levels can indicate insulin resistance, a risk factor for type 2 diabetes.
  3. C-Peptide Test:

    • Purpose: To measure the level of C-peptide, a byproduct of insulin production.
    • Why Is It Ordered: To assess how much insulin the body is producing. This is particularly relevant in distinguishing between type 1 and type 2 diabetes.
  4. Lipid Profile:

    • Purpose: To measure levels of cholesterol and triglycerides.
    • Why Is It Ordered: To assess cardiovascular risk, as diabetes is a risk factor for heart disease. Dyslipidemia often co-occurs with diabetes.
  5. Complete Blood Count (CBC):

    • Purpose: To evaluate overall blood health.
    • Why Is It Ordered: To check for signs of anemia or infection, which can sometimes be related to diabetes or its complications.
  6. Kidney Function Test:

    • Purpose: To assess kidney function.
    • Why Is It Ordered: To evaluate the kidneys, as diabetes can lead to kidney damage over time.
  7. Urinalysis:

    • Purpose: To analyze various components of the urine.
    • Why Is It Ordered: To check for glucose or ketones in the urine, which can occur in diabetes, and to evaluate overall kidney health.
  8. Thyroid Function Tests:

    • Purpose: To assess thyroid function.
    • Why Is It Ordered: Because thyroid disorders can affect metabolism and may coexist with diabetes.

These tests, when ordered alongside a 2 Specimen Glucose Tolerance Test, provide a comprehensive assessment of glucose metabolism, risk of diabetes, and related metabolic and endocrine functions. They are crucial for accurately diagnosing diabetes, identifying individuals at risk for diabetes, and managing metabolic health. The specific combination of tests will depend on the individual’s symptoms, risk factors, and medical history.

Conditions where a 2 Specimen Glucose Tolerance test is recommended:

The Glucose Tolerance Test, 2 Specimens, is vital in diagnosing and monitoring:

  • Diabetes Mellitus: This test can determine whether an individual has diabetes or pre-diabetes, aiding in early intervention and management.

  • Gestational Diabetes: Pregnant women may undergo this test to identify gestational diabetes, which can impact both maternal and fetal health.

How does my health care provider use a 2 Specimen Glucose Tolerance test?

A blood glucose test can be used for a variety of purposes, including:

  • Detect hyperglycemia and hypoglycemia
  • Screen for diabetes in those who are at risk before symptoms appear; there may be no early indications or symptoms of diabetes in some circumstances. As a result, screening can aid in detecting it and allowing treatment to begin before the illness worsens or complications emerge.
  • Aid in the detection of diabetes, prediabetes, and gestational diabetes.
  • Monitor your blood sugar levels and manage your diabetes

Glucose levels should be monitored in those who have been diagnosed with diabetes.

Between the 24th and 28th week of pregnancy, glucose blood tests are performed to assess pregnant women for gestational diabetes. Pregnant women who have never been diagnosed with diabetes should be screened and diagnosed using either a one-step or two-step strategy, according to the American Diabetes Association and the US Preventive Services Task Force.

Other tests, including diabetic autoantibodies, insulin, and C-peptide, may be used in conjunction with glucose to assist in detecting the reason of elevated glucose levels, differentiate between type 1 and type 2 diabetes, and assess insulin production.

What do my glucose test results mean?

High blood glucose levels are most commonly associated with diabetes, but they can also be caused by a variety of other diseases and ailments.

Hypoglycemia is defined by a drop in blood glucose to a level that triggers nervous system symptoms before affecting the brain.

Most Common Questions About the 2 Specimen Glucose Tolerance Test test:

Purpose and Applications

What is the primary objective of the 2 Specimen Glucose Tolerance test?

The 2 Specimen Glucose Tolerance test aims to assess how efficiently the body processes glucose. It helps in diagnosing or ruling out diabetes and prediabetes.

Why might a doctor order the 2 Specimen Glucose Tolerance test?

A doctor might order this test if a patient presents symptoms suggestive of diabetes, or if they have risk factors for diabetes. Additionally, the test can be used to monitor the glucose tolerance of individuals previously diagnosed with prediabetes.

Clinical Significance

What conditions or diseases can the 2 Specimen Glucose Tolerance test help diagnose?

The test primarily assists in diagnosing diabetes, both Type 1 and Type 2. It can also identify prediabetes, which indicates a heightened risk for the future development of diabetes.

What is the significance of abnormal results in the 2 Specimen Glucose Tolerance test?

Abnormal results can indicate impaired glucose tolerance. High levels post glucose intake suggest that the body isn't efficiently processing glucose, leading to elevated blood sugar, a hallmark of diabetes. Conversely, unusually low levels could indicate an overactive insulin response.


How are results of the 2 Specimen Glucose Tolerance test typically presented?

Results are usually given in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Baseline (fasting) glucose levels are presented alongside levels recorded after the glucose intake, typically 2 hours post-consumption.

How do healthcare providers interpret the results of the 2 Specimen Glucose Tolerance test?

A normal response is when the blood sugar rises shortly after drinking the glucose solution and then drops back to normal levels. High glucose levels 2 hours after drinking the solution may suggest diabetes or prediabetes, based on the specific values.

Clinical Limitations

How does the 2 Specimen Glucose Tolerance test compare with other glucose tests?

While the 2 Specimen Glucose Tolerance test provides detailed insights into glucose processing over time, other tests, like the A1C test, provide information about average blood sugar levels over the past 2-3 months. Each test has its specific uses, benefits, and limitations.

What can impact the accuracy of the 2 Specimen Glucose Tolerance test results?

Several factors can influence the test's accuracy, including recent food intake, physical activity, medications, and acute stress. That's why it's typically required to fast overnight before the test.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

Customer Reviews