Prenatal care
The glucose test in pregnancy: what to expect, step by step
April 27, 2026 · 7 min read
Somewhere between 24 and 28 weeks, most prenatal checklists include a glucose test, and most first-time moms have the same questions. What is the drink like? Why an hour in the waiting room? And what does it mean if they call you back? Here is the whole experience, demystified, so you walk in knowing exactly what to expect.
Why pregnancy includes a glucose test at all
During pregnancy, hormones from the placenta make your body naturally more resistant to insulin, the hormone that moves sugar out of your blood. For most people the body keeps up. For some it does not, and blood sugar runs higher than it should. That condition is called gestational diabetes, and it usually has no symptoms you would notice on your own. That is exactly why screening exists: it catches something quiet and very treatable before it can affect you or your baby's growth.
When it happens: around 24 to 28 weeks
The American College of Obstetricians and Gynecologists recommends screening for gestational diabetes at 24 to 28 weeks of pregnancy (ACOG), which is when placental hormones rise enough for the condition to show up. If you have risk factors such as a prior pregnancy with gestational diabetes, your provider may screen you earlier in pregnancy too, and then repeat the test in this window. Your clinic will tell you whether you need to do anything special beforehand; for the 1 hour screen, most do not ask you to fast.
The drink and the 1 hour test, honestly described
At the appointment you drink a small bottle of a very sweet liquid called glucola, usually orange, lemon-lime, or fruit punch flavored. Most people describe it as flat soda syrup: not delicious, but over in a few minutes. You drink it within about five minutes, then wait one hour without eating, drinking anything else, or leaving the office. At the one hour mark, a quick blood draw from your arm measures how your body handled the sugar. Then you go home. Bring a snack for after the draw and something to read for the wait.
If you are called back: the 3 hour test
If your 1 hour number is above your clinic's cutoff, the next step at most US clinics is a 3 hour glucose tolerance test. This one starts with fasting overnight. You get a blood draw on arrival, then drink a stronger glucose drink, then have your blood drawn again at one, two, and three hours. It is a long morning, so plan a quiet day, bring water for after, and arrange a ride or company if that helps you. A diagnosis of gestational diabetes is typically made only when two or more of those values come back elevated.
A positive screen is not a diagnosis
This is the sentence worth remembering in the waiting room: failing the 1 hour test does not mean you have gestational diabetes. The 1 hour test is a screen, deliberately set to catch anyone who might need a closer look, so many people who screen positive go on to pass the 3 hour test completely. Getting called back means your care team is being careful, not that something is wrong.
If the diagnosis is gestational diabetes
Even then, this is one of the most manageable conditions in pregnancy. Most people manage it with changes to meals, regular movement, and checking blood sugar at home; some also need medication, which your provider will walk you through. Blood sugar that is well controlled dramatically lowers the risks for you and your baby. After delivery, gestational diabetes usually resolves, though it does raise your risk of type 2 diabetes later in life (CDC), so follow-up testing after the birth matters. Every question about your own results belongs with your own provider, and any urgent concern in pregnancy means calling your provider or, in an emergency, 911.
Frequently asked questions
- Do I need to fast before the 1 hour glucose test?
- Usually not, but clinics differ, so follow your own clinic's instructions. Many providers suggest eating normally and skipping a sugary breakfast right before. The 3 hour test is different: that one requires fasting overnight.
- What if the drink makes me feel sick?
- Feeling a little queasy after that much sugar at once is common. If you actually vomit, tell the staff, because the test may need to be rescheduled or your provider may offer an alternative way to screen. Mention any past trouble with the drink before your appointment.
- How can Materna help me with this test?
- The Mommy Passport, free for patients, keeps your screening dates, results, and questions in one bilingual record on your phone, in English or Spanish, so whichever clinic you visit next can see your full history. It is education and record-keeping, not medical advice; your provider interprets your results.