1 Hour OGTT vs. 3-Hour Glucose Tolerance Test: Key Differences & What to Expect

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So, you’ve just taken the glucose challenge test (1-hour glucose tolerance test), and now you’re staring at the results, full of questions. What does it mean for your blood glucose level? Do you need to take the 3-hour test? Don’t worry—you’re not alone!

Let’s break down the key differences between the 1-hour and 3-hour glucose tests, what the results mean, and what to expect if you need further testing.

1-Hour vs. 3-Hour Glucose Tolerance Test: The Main Differences

1. Test Duration: A Quick Check vs. A Longer Evaluation

The 1-hour glucose test, also known as the glucose screening test, is like a quick preview—a short screening designed to flag potential gestational diabetes (GD). You drink a 50g glucose solution, wait an hour, and have one blood sample taken. That’s it!

However, the 3-hour glucose test is more in-depth. If your 1-hour test results are elevated, you’ll take the 3-hour version, which involves drinking a 100g glucose solution and undergoing four blood draws over three hours. This test provides a definitive diagnosis of gestational diabetes.

2. Sugar Intake: 50g vs. 100g of Glucose

Both tests involve drinking a sugary solution called glucose drink, but the amount of sugar varies:

  • The 1-hour test has 50g of glucose (about 12 teaspoons of sugar—way more than most people consume in one sitting!).

  • The 3-hour test contains 100g of glucose, making it a bigger challenge for your body to process.

3. Fasting Requirements: Can You Eat Before the Test?

One major difference is whether or not you need to fast before testing, which can affect your blood sugar level:

  • 1-hour test: No fasting required—you can eat normally beforehand.

  • 3-hour test: Requires fasting for at least 8-12 hours before drinking the glucose solution.

4. Blood Draws: One vs. Four

  • 1-hour test: One blood draw after 60 minutes.

  • 3-hour test: Four blood draws—one before drinking the glucose, then every hour for three hours.

Since you’ll be sitting for a while during the 3-hour test, bring a book or something to do while you wait!

5. Purpose: Screening vs. Diagnosis

The 1-hour glucose test is just a glucose screening tool. If you “fail” this test, it doesn’t necessarily mean you have a condition called gestational diabetes—it just means you need further testing.

The 3-hour glucose test is used to diagnose gestational diabetes based on your blood sugar levels over time.

What If You Fail the 1-Hour Test?

First, don’t panic! Failing the 1-hour glucose test does not mean you have gestational diabetes. Failing the 1-hour glucose test may indicate impaired glucose tolerance, which requires further testing. Many people fail the 1-hour test but go on to pass the 3-hour test with normal results.

However, if your 3-hour test confirms gestational diabetes, don’t worry—you’re not alone. With the right diet, exercise, and support, you can manage GD effectively and have a healthy pregnancy.

Need Support? You're Not Alone!

Gestational diabetes can feel overwhelming, but you don’t have to go through it alone. The HIgedi app is designed to connect you with other mamas on the same journey, all sharing meal and snack ideas, real-life plates, and blood glucose results after eating these meals. Since diet plays a huge role in managing GD, having a support buddy who understands what you’re going through can make all the difference. Whether you need meal inspiration or just someone to relate to, HIgedi is here to help.

Final Thoughts

Understanding the 1-hour vs. 3-hour glucose test can help reduce stress and give you more control over your health during pregnancy. Whether you’re just starting the screening process or facing a GD diagnosis, remember:

  • The 1-hour test is just a first step.

  • The 3-hour test provides clearer answers.

  • If you are diagnosed with gestational diabetes mellitus, there are plenty of resources and support to help you.