Preparing for glucose screening tests

Between 24 and 28 weeks of pregnancy, most expecting mums are asked to take a glucose screening test. It’s one of the key check-ups in the second trimester—and for good reason. This simple test helps detect signs of gestational diabetes, a common condition that can affect your pregnancy and your baby’s health if left untreated.

If you’ve never taken the test before, it’s natural to feel unsure or even anxious. This article will walk you through exactly what to expect, how to prepare, and what your results might mean.

What Is the Glucose Screening Test?

The glucose screening test (also called the Glucose Challenge Test or GCT) is used to check how your body processes sugar. It helps identify women who might be at risk for gestational diabetes—a temporary form of diabetes that can develop during pregnancy.

Gestational diabetes doesn’t usually have noticeable symptoms, which is why screening is so important. If caught early, it can be well-managed with diet, exercise, and sometimes medication, ensuring a healthy pregnancy and birth.

What to Expect During the Test

In most cases, your test will be done in a pathology collection centre or a hospital clinic. The standard first test involves the following steps:

1. You’ll be given a sweet glucose drink (usually orange or lemon-lime flavoured). It contains 50–75 grams of glucose.
2. You’ll wait for 1–2 hours, depending on the specific test ordered.
3. Your blood will be drawn, typically once (or multiple times, if doing the longer test).
4. Your blood sugar levels are then measured to see how your body responded.

There are two common types of tests:

• Glucose Challenge Test (GCT): This is a shorter, non-fasting test done first. If your results are elevated, you may be asked to do the longer Glucose Tolerance Test.
• Glucose Tolerance Test (GTT): A longer, fasting version that involves multiple blood draws over 2–3 hours. Some providers go directly to this test based on your risk factors or local guidelines.

Do You Need to Fast Before the Test?

This depends on the type of test your doctor has ordered:

• For the GCT (short version): Fasting is usually not required, but it’s best to avoid sugary foods or large meals right before your appointment.
• For the GTT (longer version): You’ll be asked to fast for 8–12 hours beforehand. You can usually drink plain water during this time.

Always confirm instructions with your healthcare provider or pathology centre ahead of your appointment.

How to Prepare for the Glucose Test

• Schedule the test for a time that works best with your fasting or eating routine, especially if you’re doing the longer version.
• Wear comfortable clothes with sleeves that roll up easily, as you’ll need to have your blood drawn.
• Bring water and something to read or watch—you may be sitting in the clinic for up to 2–3 hours.
• Bring a snack to eat afterwards, especially if you’ve been fasting. Many women feel light-headed or tired after the test.
• Avoid strenuous activity before the test, as it may affect your results.

What Happens If You Test Positive?

A positive result on the glucose challenge test doesn’t mean you definitely have gestational diabetes—it just means you’ll need further testing (usually the GTT) to confirm.

If you are diagnosed with gestational diabetes:

• Your care team will work with you to manage it through diet, physical activity, and regular monitoring.
• In many cases, gestational diabetes goes away after birth, though it’s important to keep an eye on future risk.

Managing it well helps reduce the chance of complications like high birth weight, preterm birth, or high blood pressure.

Emotional Side of the Test

It’s okay to feel nervous about this test—especially if you don’t like needles or worry about your results. Remember:

• Testing is not a judgment—it’s about protecting your and your baby’s health.
• Gestational diabetes is very common and not caused by anything you did wrong.
• You are not alone. Many mums navigate this and go on to have healthy, smooth births.

Talk to your midwife or doctor if you feel anxious or overwhelmed—they’re there to support you, not just medically but emotionally too.