3-Hour Glucose Tolerance Test

The 3-hour glucose tolerance test is an essential diagnostic tool used to assess how your body processes sugar and confirm whether you have gestational diabetes (diabetes during pregnancy). This test is recommended if your 1-hour glucose screening results are abnormal.

Knowing what to expect during the test, why it's important, and how to interpret the results can help ease any concerns and prepare you for the process.

If the 3-hour glucose test confirms a diagnosis of gestational diabetes, it’s important to understand this condition is not your fault. Pregnancy hormones can impact how your body uses insulin, leading to elevated blood sugar levels. Elevated blood sugar levels can happen regardless of your prior health or lifestyle choices. With the proper care, most women manage gestational diabetes successfully and go on to have healthy pregnancies.

What to Expect During the 3-Hour Glucose Tolerance Test

The 3-hour glucose tolerance test requires a total of four blood draws over three hours. The test will take place in the lab, so be prepared to block out enough time for the appointment. Here’s a step-by-step overview of what to expect:

• Fasting Blood Draw: After fasting for 8-12 hours (no food or drink except water), a blood sample will be drawn to measure your fasting glucose level.
  
  
• Drinking the Glucose Solution: After the fasting blood draw, you will be given a glucose drink containing a specific amount of sugar. You must consume this within 5 minutes.
  
  
• Timed Blood Draws: Your blood will be drawn 1 hour, 2 hours, and 3 hours after drinking the glucose solution. These measurements will show how your body processes sugar over time.

Download our 3-Hour Glucose Tolerance Test Instructional PDF here!

How to Prepare for the 3-Hour Glucose Tolerance Test

Proper preparation can ensure accurate results and make your test experience more comfortable. Here are some helpful tips:

• Eat Normally Leading Up to the Test: Maintain your regular diet before the day of testing.
  
  
• Fast for 8-12 Hours: Do not eat, drink, smoke, or exercise during this time. You may drink plain water.
  
  
• Plan for the Time Commitment: The test will take up to 4 hours. Activity can interfere with results, so you will need to remain in the lab for the duration. Be sure to bring a book, podcast, or project to keep yourself occupied.
  
  
• Stay Hydrated: You may drink water during the test. Feel free to bring a water bottle.
  
  
• Bring a Snack: You may feel hungry once the test is complete. Bring a light snack to eat afterward.

Understanding Your Results

Gestational diabetes is typically diagnosed when two or more of the blood results are elevated above the general levels listed below:

• Fasting: Less than 95 mg/dL
• 1 Hour: Less than 180 mg/dL
• 2 Hours: Less than 155 mg/dL
• 3 Hours: Less than 140 mg/dL

Your provider will review your results and explain what they mean. If your results indicate gestational diabetes, your care team will partner with you to create a personalized management plan to ensure the best outcomes for you and your baby.

What Happens If You Fail the 3-Hour Glucose Test?

If you’re diagnosed with gestational diabetes, it’s important to know this condition is manageable and temporary. In most cases, blood sugar levels return to normal shortly after delivery as hormone levels stabilize. If needed, your doctor may make the following suggestions to help manage the condition throughout your pregnancy:

• Nutrition Counseling: You may be referred to a dietitian to help develop a meal plan to stabilize blood sugar levels.
  
  
• Monitoring Blood Sugar Levels: You will need to check your blood sugar regularly with a glucometer.
  
  
• Physical Activity Recommendations: Your provider may recommend light exercises like walking to help your body use insulin more effectively.
  
  
• Potential Medication: In some cases, insulin or oral medications may be needed to help control blood sugar.

Remember, gestational diabetes is not a reflection of something you did wrong. Hormonal changes during pregnancy can cause this condition, and with proper care, most women go on to have healthy pregnancies and babies.