Glucose Tolerance Test- 2 Hrs (3 Samples)

Diabetes

Report in 4Hrs

At Home

Fasting Required

Details

Checks glucose metabolism.

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Glucose Tolerance Test - 2 Hrs (3 Samples)

Why is it done?
- Measures the body's ability to regulate blood glucose levels by monitoring glucose response to a standardized sugar load over a 2-hour period with 3 timed blood samples (fasting, 1-hour, and 2-hour)
- Screens for gestational diabetes mellitus (GDM) in pregnant women, typically performed between 24-28 weeks of gestation
- Diagnoses Type 2 diabetes mellitus and impaired glucose tolerance in non-pregnant individuals
- Identifies individuals at risk for prediabetes or metabolic syndrome
- Evaluates patients presenting with symptoms suggestive of diabetes or glucose regulation disorders
- Assesses glucose tolerance in individuals with family history of diabetes or metabolic risk factors
Normal Range
- Fasting Blood Glucose (Sample 1): Less than 95 mg/dL (5.3 mmol/L) - Normal
- 1-Hour Post-Glucose Load (Sample 2): Less than 180 mg/dL (10.0 mmol/L) - Normal
- 2-Hour Post-Glucose Load (Sample 3): Less than 140 mg/dL (7.8 mmol/L) - Normal
- For Gestational Diabetes Screening (75g load):
- Fasting: Less than 92 mg/dL (5.1 mmol/L)
- 1-Hour: Less than 180 mg/dL (10.0 mmol/L)
- 2-Hour: Less than 153 mg/dL (8.5 mmol/L)
- Units of Measurement:
- mg/dL (milligrams per deciliter) or mmol/L (millimoles per liter)
- Normal results indicate appropriate glucose regulation and absence of diabetes or impaired glucose tolerance
Interpretation
- Normal Glucose Tolerance: All three values within normal limits; indicates effective glucose regulation and absence of diabetes
- Impaired Fasting Glucose: Fasting glucose 100-125 mg/dL; indicates prediabetes and elevated diabetes risk
- Impaired Glucose Tolerance: 2-hour glucose 140-199 mg/dL; indicates glucose regulation deficiency and prediabetic state
- Type 2 Diabetes Mellitus: Fasting ≥126 mg/dL or 2-hour ≥200 mg/dL; confirms diabetes diagnosis (requires confirmation on separate day)
- Gestational Diabetes Mellitus (GDM) Diagnosis: Two or more values meeting or exceeding cutoff thresholds on 75g OGTT; confirmed diagnosis requires repeat testing
- Factors Affecting Results:
- Recent illness, infection, or stress may elevate glucose levels
- Medications (corticosteroids, diuretics, beta-blockers) can affect glucose tolerance
- Inadequate fasting or improper preparation may yield false results
- Physical inactivity and increased sedentary time before testing may impair glucose tolerance
- Pancreatitis, liver disease, or kidney dysfunction may alter test results
- Age, body weight, and pregnancy status influence glucose response patterns
Associated Organs
- Primary Organ Systems:
- Pancreas - produces insulin necessary for glucose regulation; dysfunction leads to abnormal glucose tolerance
- Liver - plays critical role in glucose metabolism and storage; regulates blood glucose through glycogenolysis and gluconeogenesis
- Muscle and adipose tissues - primary insulin-responsive tissues; insulin resistance compromises glucose uptake
- Common Associated Conditions:
- Type 2 Diabetes Mellitus - chronic metabolic disorder characterized by insulin resistance and progressive beta cell dysfunction
- Gestational Diabetes Mellitus - temporary hyperglycemia occurring during pregnancy; increases lifelong diabetes risk
- Prediabetes - intermediate glucose dysfunction increasing Type 2 diabetes risk substantially
- Metabolic Syndrome - cluster of conditions including central obesity, hypertension, and dyslipidemia linked to impaired glucose tolerance
- Polycystic Ovary Syndrome (PCOS) - endocrine disorder frequently associated with insulin resistance and glucose intolerance
- Cushing's Syndrome - elevated cortisol impairs glucose tolerance and increases diabetes risk
- Potential Complications of Abnormal Results:
- Microvascular complications - diabetic retinopathy, nephropathy, and neuropathy with chronic hyperglycemia
- Macrovascular complications - increased cardiovascular disease, stroke, and peripheral vascular disease risk
- Fetal complications in GDM - macrosomia, neonatal hypoglycemia, and increased cesarean delivery risk
- Maternal complications in GDM - preeclampsia, polyhydramnios, and increased infection risk
Follow-up Tests
- If Abnormal Results Are Found:
- Fasting Blood Glucose (FBG) - confirm diagnosis and assess baseline glycemic control
- Hemoglobin A1C (HbA1c) - evaluate long-term glucose control over 2-3 months; assists diabetes diagnosis and monitoring
- Fasting Insulin Level - assess degree of insulin resistance and pancreatic function
- C-peptide Test - evaluate pancreatic beta cell function and residual insulin secretion capacity
- Lipid Panel - assess lipid metabolism abnormalities frequently associated with glucose intolerance
- Liver Function Tests - evaluate hepatic glucose metabolism and exclude liver disease
- Renal Function Tests - screen for early diabetic kidney disease and assess baseline renal function
- Urine Microalbumin - detect early diabetic nephropathy in glucose-intolerant patients
- For GDM Diagnosis Confirmation:
- Repeat Oral Glucose Tolerance Test - confirm diagnosis on separate occasion with 3-hour extended testing
- Obstetric Ultrasound - monitor fetal growth and assess for complications of maternal hyperglycemia
- Continuous Glucose Monitoring - track glucose patterns throughout pregnancy if GDM confirmed
- Monitoring Frequency:
- Normal results - retest every 3 years or as recommended for continued diabetes surveillance
- Prediabetes - repeat testing annually or more frequently with lifestyle interventions
- Confirmed diabetes - regular HbA1c monitoring every 3 months until stable, then every 3-6 months
- GDM - postpartum glucose testing 6-12 weeks after delivery and annual screening thereafter
Fasting Required?
- Yes - Fasting is REQUIRED for this test
- Fasting Duration: 8-12 hours before initial blood draw; optimal is 8-10 hours overnight fast
- What Fasting Means:
- No food or caloric beverages (including juice, soda, coffee with cream/sugar) for 8-12 hours before first blood sample
- Water intake is permitted and encouraged throughout fasting period
- Plain black coffee or tea without additives is generally acceptable but verify with testing facility
- Medications:
- Continue regular medications unless specifically instructed otherwise by physician
- Inform healthcare provider of all medications, especially corticosteroids, diuretics, and beta-blockers which may affect results
- Do not take diabetes medications (oral agents or insulin) before the test; administer after completion of test
- Test Duration and Procedure:
- Total test duration is approximately 2 hours at testing facility
- First blood draw (fasting sample) taken after 8-12 hour fast; then ingest 75g glucose solution (or 100g for GDM)
- Glucose solution consumed over 5 minutes; some patients experience mild nausea or sweet taste sensitivity
- Second blood draw at exactly 1 hour after glucose ingestion
- Third blood draw at exactly 2 hours after glucose ingestion to complete 3-sample panel
- Other Patient Preparation Requirements:
- Avoid strenuous exercise for 24 hours before testing; may alter glucose metabolism
- Maintain regular diet for 3 days prior to test; sudden dietary changes may affect glucose response
- Get adequate sleep night before testing; sleep deprivation impairs glucose regulation
- Manage stress before test; psychological stress elevates cortisol and glucose levels
- Reschedule test if acutely ill, experiencing infection, or recently hospitalized as these affect glucose tolerance
- Bring insurance card and identification; arrange transportation as test requires 2-hour commitment at facility
- Wear comfortable clothing; blood pressure and weight may be checked during visit

How our test process works!