Glucose Tolerance Test in Pregnancy: What to Expect and Why It Matters

If you’re pregnant, you’ve probably heard about the glucose tolerance test pregnancy involves, but here’s what nobody tells you: it’s not a sign something is wrong with you. It’s a smart screening that catches how your body is handling sugar during a time when everything metabolically shifts — because pregnancy demands more insulin, and sometimes that system needs support.

Most pregnant people dread the syrupy drink and the wait for results, but understanding what this test actually does — and why it matters — can transform it from anxiety-inducing to genuinely reassuring. Between 24 and 28 weeks, your care team will likely ask you to take a glucose tolerance test, and this guide walks you through exactly what to expect, how to prepare, and what your results actually mean for you and your baby.

What Is a Glucose Tolerance Test During Pregnancy?

Here’s the honest truth: nobody loves hearing they need a glucose test. The fasting, the syrupy drink, the waiting — it’s a lot when you’re already tired.

But here’s what I know about it. The glucose tolerance test during pregnancy is a standard screening that checks how well your body is processing sugar. It’s not because something is wrong. It’s because pregnancy changes everything about your metabolism, and your care team needs to see what’s happening.

Your body needs more insulin during pregnancy to keep up with the demands of a growing baby. Sometimes, that system doesn’t keep pace. That’s gestational diabetes — and the only way to catch it is to look for it.

The ACOG recommends screening all pregnant women for gestational diabetes between 24 and 28 weeks of pregnancy. If you have risk factors — like a family history of diabetes or a higher BMI — your provider may test earlier than that.

There are two versions of the test. The first is a one-hour screening where you drink a glucose solution and have one blood draw. If that result comes back elevated, you move on to a longer three-hour test, which is the one that actually confirms a diagnosis.

It’s worth knowing what you’re eating in the weeks around this test too. If you’re thinking through your prenatal nutrition more broadly, the guide on what to eat in early pregnancy first trimester is a good place to start.

The test isn’t fun. But catching gestational diabetes early — before it has a chance to affect you or your baby — is genuinely worth the two hours of your life.

When Do You Get a Glucose Tolerance Test in Pregnancy?

For most pregnancies, the glucose tolerance test happens between 24 and 28 weeks. That window isn’t random — it’s when your placenta is producing enough hormones to potentially interfere with how your body uses insulin.

Before that point, gestational diabetes simply wouldn’t show up reliably. After it, you’d lose valuable time to manage it safely. The timing is deliberate, and it matters.

The ACOG recommends that all pregnant people be screened for gestational diabetes between 24 and 28 weeks of pregnancy — because catching it in this window gives you and your care team the best chance to protect your baby’s growth and your own health before delivery.

If you’re considered higher risk — carrying multiples, have a history of gestational diabetes, a BMI over 30, or a family history of type 2 diabetes — your provider may test you much earlier. Sometimes as early as the first trimester.

An early normal result doesn’t mean you’re done. You’ll still be retested at the standard 24–28 week mark. Because risk can change as your pregnancy progresses.

It can feel a little strange to be tested for something when you feel completely fine. That’s actually the whole point. Gestational diabetes often has no symptoms you’d notice on your own.

What you’re eating around this time is worth thinking about too. Not because food choices cause the test result, but because your overall prenatal nutrition picture matters for so much more than just this screening. If you’re still figuring that side of things out, the guide on foods to avoid during pregnancy is a straightforward place to start.

Your provider will walk you through the prep instructions specific to you. But knowing the timing in advance means you won’t be caught off guard when the appointment comes up.

How the Glucose Tolerance Test Works: Step by Step

Here’s what actually happens at the appointment, because knowing ahead of time makes it so much easier to walk in calm.

When you arrive, a nurse draws your blood to get a baseline reading. Then you drink a small bottle of glucose solution — usually 50 grams of sugar dissolved in liquid.

The taste? Most people describe it as flat, very sweet orange soda. Some find it totally fine. Some feel a little queasy. Both are normal, and it goes down fast.

After you drink it, you wait exactly one hour. You’ll stay at the clinic — sitting, reading, scrolling your phone. Nothing strenuous. Then they draw your blood again to see how your body processed the sugar.

The ACOG recommends that all pregnant people be screened for gestational diabetes, typically between 24 and 28 weeks, because early identification leads to better outcomes for both you and your baby.

For the one-hour screening, a blood sugar result under 140 mg/dL is generally considered normal. If your number comes back higher than that, it doesn’t mean you have gestational diabetes — it means you move on to the three-hour test for a closer look.

A lot of women pass the one-hour screening without any issue. Some don’t, and that’s what the follow-up is for. One number is not a diagnosis.

The glucose tolerance test during pregnancy sounds more intense than it actually is. The hardest part for most people is the waiting — and maybe the sweetness of the drink if you’re already dealing with any nausea. If morning sickness remedies are still part of your daily routine at this point, let your provider know before the test so they can advise you on what to do.

The whole thing from first blood draw to last is usually done within 90 minutes. Then you go home.

Preparing for Your Glucose Tolerance Test

Here’s the thing nobody tells you clearly: for the standard one-hour glucose tolerance test in pregnancy, you don’t need to fast. Eat normally beforehand. Skipping meals trying to “help” your results can actually work against you.

What you eat in the days leading up to the test doesn’t need to change either. Don’t crash-diet or carb-restrict to try to influence the numbers. Your provider needs to see how your body handles glucose on a normal day — not a curated one.

Wear something comfortable with easy access to your inner arm. You’ll have at least one blood draw, sometimes two, and wrestling with tight sleeves gets old fast.

Bring something to do. Seriously. You’ll drink the glucose solution, then wait an hour before your blood is drawn. That waiting room hour is yours — a podcast, a book, a long scroll through your phone. No shame in it.

A few things worth knowing before you go: the drink is very sweet, almost syrupy. Most people get it down fine. Some don’t love the taste, especially if your stomach is still sensitive. Drinking it cold and through a straw can help if you’re worried.

You might feel a little jittery or lightheaded after. That’s normal. Your blood sugar spikes and your body reacts. Sit, rest, let it pass. If you feel genuinely unwell, tell the staff — they’ve seen it before.

If your provider has already mentioned keeping an eye on your activity levels, you might find it useful to read up on pregnancy safe workouts — movement can support blood sugar regulation, and knowing what’s actually safe during pregnancy takes one more worry off your plate.

Go in prepared, not anxious. You’re doing the test because your provider is paying attention. That’s a good thing.

Understanding Your Glucose Tolerance Test Results

Getting a number back without context is genuinely stressful. So let’s talk about what these results actually mean.

The one-hour screening test — the one most people do first — is not a diagnosis. It’s a flag. If your blood sugar reads below 140 mg/dL one hour after drinking the glucose solution, you’re in the clear for most providers. Some set the threshold at 130 mg/dL. Your provider will tell you which cutoff they use.

If your number comes back higher than that threshold, it doesn’t mean you have gestational diabetes. It means your body needs a closer look.

That’s where the three-hour glucose tolerance test in pregnancy comes in. This one is the diagnostic test — the one that actually tells you something. You’ll fast overnight, get your blood drawn four times over three hours, and your provider will look at the full picture of how your body processes sugar over time.

To be diagnosed with gestational diabetes, at least two of those four values need to come back elevated — not just one. One high reading alone usually isn’t enough.

The ACOG recommends that all pregnant people without a prior gestational diabetes diagnosis be screened between 24 and 28 weeks — because this is when the placental hormones that affect insulin resistance are at their peak.

If you do need the three-hour test, here’s what I want you to hold onto: most people who move on to that second test do not get a gestational diabetes diagnosis. The screening casts a wide net on purpose.

And if you do get that diagnosis? It’s manageable. Knowing is always better than not knowing — for you and for your baby. You’ll want to start thinking about what the rest of pregnancy looks like from here, including how labor may be managed. Reading up on the stages of labor and dilation can help you feel less blindsided when that conversation comes up with your provider.

Gestational Diabetes: What If Your Test Comes Back High?

First — take a breath. A gestational diabetes diagnosis feels scary, and that fear makes complete sense.

But here’s what I want you to know: this is one of the most common pregnancy complications there is. You didn’t cause it. Your body is doing something a lot of pregnant bodies do.

The glucose tolerance test in pregnancy is designed to catch this early — and catching it early is genuinely good news. You have time to manage it, monitor it, and protect yourself and your baby before birth.

For most people, management starts with diet. That means watching carbohydrates, spacing meals evenly, and pairing carbs with protein to slow your blood sugar response. It’s an adjustment, but it’s doable — and your care team will walk you through exactly what to eat.

You’ll also likely start checking your blood sugar at home with a small monitor, usually a few times a day. It sounds like a lot, but it quickly becomes routine. Most people have it down within a week.

If diet alone doesn’t bring your numbers into range, your provider may talk to you about medication — either oral or insulin. That’s not a failure. It just means your body needs a little more help, and that’s what the medication is there for.

The ACOG recommends that women with gestational diabetes receive nutritional counseling and self-monitoring of blood glucose as first-line management — because for many people, those two things alone are enough to keep numbers controlled throughout pregnancy.

And here’s the part I really want you to hold onto: gestational diabetes is temporary. For most people, blood sugar returns to normal after delivery. You’ll be tested postpartum to confirm it, but this diagnosis does not define the rest of your health story.

If you’re thinking ahead to birth and what labor might look like now, our guide on water breaking pregnancy signs is a good next read.

Why the Glucose Tolerance Test Matters for Your Baby

I know it can feel like just another box to tick. But this one genuinely matters — not just for you, but for the little one you’re growing.

When blood sugar stays too high during pregnancy, your baby’s body responds by producing extra insulin to compensate. That extra insulin acts as a growth signal.

The result? Babies born to mothers with unmanaged gestational diabetes are more likely to be larger than average — a condition called macrosomia. That can make delivery harder and increase the likelihood of a C-section or birth injury.

The ACOG notes that babies exposed to poorly controlled gestational diabetes are at higher risk for low blood sugar (hypoglycemia) immediately after birth, because their bodies were working overtime in the womb and suddenly that glucose supply is gone.

There are longer-term considerations too. Early exposure to high glucose levels in utero has been linked to a greater risk of the child developing type 2 diabetes and obesity later in life. That’s not said to frighten you. It’s said because early detection — through the glucose tolerance test in pregnancy — genuinely changes outcomes.

When you catch it early, you have time to act. Adjusting what you eat, adding movement, monitoring your numbers — these aren’t small things. They directly affect how your baby grows and how healthy they are at birth.

Your placenta, your blood, your body — it’s all connected to theirs right now. And that’s exactly why showing up for this test is one of the most protective things you can do.

If you’re also navigating other pregnancy changes alongside this, it helps to know what’s normal. Things like round ligament pain can show up around the same trimester and feel alarming if you don’t know what you’re dealing with.

Sources

• Mayo Clinic — glucose tolerance test procedure, timing, and what results indicate.
• MedlinePlus — gestational diabetes screening guidelines and test interpretation.

Frequently Asked Questions

Do I need to fast before my glucose tolerance test in pregnancy?

No — the one-hour screening test does not require fasting. You can eat and drink normally before your appointment.

However, if your screening comes back elevated and you need the three-hour diagnostic test, you will need to fast for 8–14 hours beforehand. Your provider will give you specific instructions if that happens.

What does it mean if my glucose tolerance test result is slightly elevated?

A slightly elevated result on the one-hour screening doesn’t automatically mean you have gestational diabetes. About 15–25% of pregnant people get a high screening result, and many of them do not have gestational diabetes.

Your provider will recommend the three-hour diagnostic test to see whether your glucose levels are actually elevated enough to meet gestational diabetes criteria. This follow-up test is what actually confirms a diagnosis.

Can I eat normally the day of my glucose tolerance test, or do I need to prepare?

For the one-hour screening test, eat normally. There’s no special prep needed — just show up well-rested and with your regular breakfast or snack if that’s when your appointment is scheduled.

The only thing to avoid is showing up on an empty stomach, which can make you feel faint during the test. Eating your usual meals before the test actually helps your body respond normally.

Is gestational diabetes permanent, or does it go away after pregnancy?

Gestational diabetes is temporary — it typically disappears within weeks after you deliver your baby. Your glucose metabolism returns to normal once the placenta (which produces hormones that interfere with insulin) is no longer there.

That said, having gestational diabetes does increase your risk of developing type 2 diabetes later in life. Your care team will likely recommend screening after pregnancy and lifestyle choices that support long-term glucose health.

How often will I be monitored if I’m diagnosed with gestational diabetes?

If you’re diagnosed with gestational diabetes, you’ll typically monitor your blood glucose at home using a glucose meter, usually checking levels before and after meals. Most people test 3–4 times per day.

Your provider will also schedule regular appointments to review your readings and adjust your meal plan or medication as needed. You may also have more frequent ultrasounds to monitor your baby’s growth.