Glucose Challenge Test (GCT), 1-Hour Post Glucose
About Glucose Challenge Test (GCT)
| Field | Value |
|---|---|
| Also Known As | GCT, 50g Glucose Challenge Test, One-Hour Glucose Tolerance Test, Glucose Screening Test (GST), O'Sullivan Test |
| Sample Type | Venous blood (plasma) |
| Fasting Required | No fasting required |
| Report Time | Same day to within 24 hours |
| Recommended For | Pregnant women, typically at 24 to 28 weeks of pregnancy; earlier for high-risk individuals |
| Price | Starting at ₹90 |
What Is a Glucose Challenge Test (GCT), 1-Hour Post Glucose?
The glucose challenge test (GCT) is a blood test used during pregnancy to check how the body processes sugar. Also known as the glucose screening test (GST) or O'Sullivan test, it measures blood glucose exactly one hour after drinking a glucose solution.
A doctor typically prescribes this test between 24 and 28 weeks of pregnancy as part of routine prenatal care. The sample collected is venous blood drawn from the arm.
What Does a Glucose Challenge Test (GCT) Measure?
The 1-hour glucose challenge test (GCT) measures a single value: the blood glucose level one hour after consuming a 50-gram glucose drink. This reading shows how well the body regulates blood sugar in response to a glucose load. An elevated result may indicate that the body is not processing glucose efficiently, which warrants further testing.
| Parameter | What It Shows |
|---|---|
| 1-hour post 50g glucose | Blood sugar response to a glucose load; used to screen for gestational diabetes |
Why Is a Glucose Challenge Test (GCT) Done?
The GCT test is prescribed for a specific purpose during pregnancy, but a doctor may also recommend it earlier for women at higher risk.
Common Symptoms That May Require This Test
In most cases, this test is part of routine prenatal screening rather than a response to symptoms. Occasionally, mild signs may prompt earlier testing. These include:
- No symptoms at all (most common scenario; test is done routinely)
- Increased thirst or frequent urination
- Unexplained fatigue
- Mild shakiness or dizziness
- Family history of diabetes noted at a prenatal appointment
Conditions This Test Can Help Detect
The 1-hour post glucose test is used to identify or flag the following:
- Gestational diabetes mellitus (initial screening)
- Increased risk of developing type 2 diabetes later in life
- Early indicators of cardiovascular risk linked to abnormal glucose response during pregnancy
Glucose Challenge Test (GCT) During Pregnancy
The 1-hour glucose challenge test (GCT) is a standard part of prenatal care. Women at average risk are screened between 24 and 28 weeks of pregnancy, while those at higher risk may be tested earlier. Major obstetric bodies recommend this two-step screening approach — starting with the GCT — to identify gestational diabetes in all pregnant women.
How to Prepare and What to Expect
No special preparation is needed before a GCT test, but a few simple steps can help ensure accurate results.
Do You Need to Fast?
No, fasting is not required for the 1-hour glucose challenge test (GCT). You can eat and drink normally on the day of the test. However, it is advisable to avoid an unusually high-sugar meal immediately beforehand. If additional tests are ordered alongside the GCT, those may have separate fasting requirements — confirm with your doctor.
Practical Tips Before Your Test
Keeping a few things in mind before your appointment can help the process go smoothly:
- Eat normally, but avoid a heavily sugary meal right before the test
- Inform your doctor about any medications you are taking, particularly steroids, blood pressure medicines, or antidepressants
- Avoid vigorous exercise shortly before the test, as intense physical activity can lower blood glucose
- Schedule your appointment for the morning if possible, as glucose responses can vary at different times of day
- Stay well hydrated with water
Step-by-Step Procedure
Here is what to expect from start to finish during a glucose screening test (GST):
- You arrive at the collection centre or receive a home visit from a trained phlebotomist.
- You are given a sweet liquid containing 50 grams of glucose dissolved in approximately 250 to 300 mL of water and asked to drink it.
- You wait for exactly one hour. Light sitting and resting is advised during this time.
- A small blood sample is drawn from a vein in your arm using a fine needle. The process takes only a few seconds.
- The sample is labelled and sent to the laboratory for analysis.
- Your result is processed and the report is delivered, usually on the same day or within 24 hours.
Factors That Can Affect Accuracy
Several factors can influence your GCT test result. Let your doctor know about any of the following:
- Time of day the test is done (morning testing may produce different readings than evening testing)
- Medications such as steroids, diuretics, or birth control pills
- Recent illness or significant physical or emotional stress
- Conditions such as polycystic ovary syndrome (PCOS), which is linked to insulin resistance
- Unusually high sugar intake immediately before the test
Understanding Your Glucose Challenge Test (GCT) Results
Your doctor will review your GCT test result alongside your overall health history and pregnancy details. The table below shows general reference values used to interpret this test.
| Parameter | Normal Result | Borderline (Follow-up Needed) | High (Immediate Review) |
|---|---|---|---|
| 1-hour post 50g glucose | Less than 140 mg/dL | Above 140 mg/dL | 190 mg/dL and above |
A result below 140 mg/dL is considered normal. A result of above 140 and below 190 mg/dL typically leads to a follow-up 3-hour oral glucose tolerance test (OGTT) within one week. A result of 190 mg/dL or above may be considered diagnostic of gestational diabetes without a follow-up test.
These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain factors may affect how your result is interpreted. These include:
- Body weight before and during pregnancy: higher pre-pregnancy BMI and greater weight gain during pregnancy are associated with a higher likelihood of an abnormal GCT result.
- Time of day and fasting duration: evening testing with a shorter fast tends to produce lower glucose readings compared with morning testing.
- Endocrine conditions such as hyperthyroidism (overactive thyroid), acromegaly (excess growth hormone), or Cushing's syndrome (excess cortisol) can cause abnormal glucose tolerance independent of diabetes.
How to Maintain Healthy Levels
These general wellness tips support healthy blood glucose during pregnancy:
- Eat a balanced diet with plenty of fibre and limit foods high in added sugar
- Engage in regular, moderate physical activity as approved by your obstetrician
- Aim to maintain a healthy weight before and throughout pregnancy
Lupin Diagnostics Glucose Challenge Test (GCT), 1-Hour Post Glucose Price and Home Collection
This test is available at Lupin Diagnostics with home sample collection across major Indian cities. The GCT test price varies by location. The table below shows indicative prices across major cities in India:
| City | Approximate Price (₹) |
|---|---|
| Mumbai | ₹120 |
| Pune | ₹100 |
| Bangalore | ₹100 |
| Hyderabad | ₹120 |
| Chennai | ₹120 |
| Indore | ₹90 |
| Kolkata | ₹100 |
| Bhopal | ₹90 |
Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
- Select the test on the Lupin Diagnostics website
- Choose your city and preferred time slot
- Opt for home sample collection by a certified phlebotomist, or visit your nearest Lupin Diagnostics centre
- Receive your report via email or WhatsApp within the stipulated turnaround time
Home Collection
Lupin Diagnostics offers home collection for the 1-hour glucose challenge test (GCT) across cities, so you can complete the test from the comfort of your home. All samples are processed in NABL-accredited laboratories by trained professionals. Digital reports are delivered directly to your email or WhatsApp.
Frequently Asked Questions
The glucose challenge test (GCT) is a screening test used during pregnancy to check for gestational diabetes. You drink a 50-gram glucose solution, and your blood sugar is measured exactly one hour later. It is not a diagnostic test on its own; an elevated result simply means further testing is needed.
Women at average risk typically have the GCT test done between 24 and 28 weeks of pregnancy. If you have risk factors such as obesity, a family history of diabetes, or a previous pregnancy with gestational diabetes, your doctor may recommend the test earlier.
No fasting is required before the 1-hour post glucose test. You can eat normally on the day of the test. It is sensible to avoid a very sugary meal immediately before your appointment, but there is no formal fasting restriction.
A result above 140 and below 190 mg/dL is considered borderline. Your doctor will usually arrange a follow-up 3-hour oral glucose tolerance test (OGTT) within one week to confirm or rule out gestational diabetes. A result of above 190 mg/dL may indicate gestational diabetes.
Yes. Medications such as steroids, certain diuretics, and some antidepressants can raise blood glucose and affect your GCT test reading. Always inform your doctor about every medication and supplement you are taking before the test.
No, the two tests are different. The glucose challenge test (GCT) is a quick screening test that does not require fasting and involves a single blood draw. The OGTT is a longer diagnostic test requiring an overnight fast and multiple blood draws over three hours. A raised GCT result is typically the trigger for an OGTT.
Reports for the 1-hour glucose challenge test (GCT) are usually available on the same day or within 24 hours. At Lupin Diagnostics, your report is delivered digitally via email or WhatsApp, so you do not need to visit the centre to collect it.
Glucose Challenge Test (GCT), 1-Hour Post Glucose
