At some point between picking nursery paint colors and wondering if you’ll ever see your ankles again, your prenatal provider will probably bring up something called
gestational diabetes screening. It sounds serious (and a little intimidating), but in reality it’s a very common part of routine prenatal care and it mostly involves
sitting, sipping a very sweet drink, and getting your blood drawn.
This guide walks you through exactly what to expect from gestational diabetes screening: when it happens, what the different glucose tests are, how to get ready, what the numbers mean,
and what happens next if your results are abnormal. Think of it as a friend who’s done the test already and is now giving you the honest, medically accurate play-by-play.
What is gestational diabetes, and why do we screen for it?
Gestational diabetes (GDM) is a type of diabetes that first appears during pregnancy. Hormones from the placenta can make your body more resistant to insulin, the hormone that helps keep
blood sugar in a healthy range. Some pregnant people’s bodies can’t keep up with that change, so blood sugar levels climb higher than normal.
Untreated or poorly controlled gestational diabetes can increase the risk of:
- Having a larger-than-average baby (macrosomia), which can make birth more complicated
- High blood pressure and preeclampsia during pregnancy
- Preterm birth or need for a C-section
- Low blood sugar (hypoglycemia) in the baby shortly after birth
- Both you and your child having a higher risk of type 2 diabetes later in life
The good news: when gestational diabetes is found early through screening and treated, many of these risks can be significantly reduced. That’s why major organizations like the
American College of Obstetricians and Gynecologists (ACOG), the American Diabetes Association (ADA), and the U.S. Centers for Disease Control and Prevention (CDC) recommend
routine screening for most pregnancies in the U.S.
When does gestational diabetes screening usually happen?
For most pregnant people, gestational diabetes screening happens between 24 and 28 weeks of pregnancy. That’s roughly late second trimester the “I can still see my feet but
tying my shoes is becoming an Olympic sport” stage.
Why that window? That’s about the time gestational diabetes typically develops. Screening then gives your provider enough time to confirm a diagnosis, help you manage blood
sugar, and monitor your baby’s growth as the pregnancy continues.
Your provider might recommend earlier screening (often in the first trimester) if you have higher-risk factors, such as:
- Obesity or higher body mass index (BMI)
- History of gestational diabetes in a previous pregnancy
- Having delivered a previous baby over 9 pounds
- Prediabetes or type 2 diabetes risk factors before pregnancy
- Strong family history of type 2 diabetes
Even if early screening is normal, many people are retested at 24–28 weeks because hormone levels change as pregnancy progresses.
The main tests used for gestational diabetes screening
In the U.S., you’ll usually encounter one of two general strategies:
a two-step approach (most common) or a one-step approach. Both are forms of glucose tolerance tests, sometimes called a “glucose challenge test” or simply “that orange drink test.”
Step 1: The 1-hour glucose challenge test (screening test)
The 1-hour glucose challenge test is often the first step. It’s a screening test, not a final diagnosis.
Here’s how it typically works:
-
No fasting needed (in most cases). Unlike some blood tests, you can usually eat normally beforehand unless your clinic gives different instructions. That said, many people find it
more comfortable not to show up right after a donut run. -
You drink a glucose solution. A nurse or technician gives you a bottle with 50 grams of glucose dissolved in flavored liquid. It often tastes like very sweet sports drink or
flat soda. You’re asked to drink it within a few minutes. - You wait for 1 hour. During this time, your body absorbs the sugar, and your blood sugar rises. You’ll usually stay at the lab or clinic.
- Blood draw. After 60 minutes, a blood sample is drawn from your arm to check your blood glucose level.
Your result is compared with a cutoff value used by that lab or clinic. If your blood sugar is below the cutoff, you “pass” the screening and usually don’t need more testing.
If it’s above, it doesn’t mean you definitely have gestational diabetes it just means you’ll be asked to come back for a more detailed test.
Step 2: The 3-hour oral glucose tolerance test (diagnostic test)
If your 1-hour screening is elevated, the next step is often a 3-hour oral glucose tolerance test (OGTT) with a larger sugar load (often 100 grams of glucose). This test is designed
to diagnose gestational diabetes more definitively.
Here’s what usually happens:
- You fast overnight. Typically you don’t eat or drink anything except water for 8–12 hours before the test.
- Fasting blood draw. When you arrive, the lab draws your blood to measure your fasting blood sugar level.
- You drink a stronger glucose solution. This one is sweeter than the 1-hour drink and contains more glucose.
-
Multiple blood draws. Your blood will usually be drawn at 1, 2, and 3 hours after you finish the drink. These four values (fasting, 1-hour, 2-hour, and 3-hour) are compared to
diagnostic cutoffs.
If two or more of these values are above the recommended thresholds used by your provider’s guidelines, you’ll be diagnosed with gestational diabetes. Different professional
groups use slightly different cutoff numbers, which is why your provider might emphasize that they’re following a specific guideline (for example, ACOG or ADA recommendations).
The one-step 75-gram OGTT
Some practices use a one-step approach instead. In that case, you:
- Fast overnight
- Have a baseline blood draw
- Drink a 75-gram glucose solution
- Have your blood drawn again at set intervals (commonly 1 and 2 hours afterward)
If any one of those values is above guideline-specific cutoffs, gestational diabetes may be diagnosed. This approach is also recognized by major diabetes organizations and is
used more commonly in some countries and some U.S. practices.
How to prepare for gestational diabetes screening
Your provider or lab will give you specific instructions those always come first. But in general:
For the 1-hour glucose challenge test
- Fasting usually isn’t required. Many clinics allow you to eat normally beforehand.
-
Light, balanced meal is your friend. Some people feel better if they avoid very high-sugar, high-carb meals immediately before the test (think giant stacks of pancakes with syrup)
so they don’t feel extra nauseous. - Bring a snack for afterward. Once the blood draw is done, a protein-rich snack can help you feel more normal again.
For the 3-hour or 75-gram OGTT
- Plan for fasting. Expect no food or flavored drinks for 8–12 hours before the test water is usually allowed.
- Ask about medications. Some medicines can affect blood sugar. Don’t stop anything without asking, but do tell your provider what you’re taking.
- Block off your schedule. You’ll be at the lab for about 2–3 hours, so bring something to read, watch, or listen to.
If you feel very nauseated during pregnancy, let your provider know. They may be able to schedule the test earlier in the day, adjust timing, or suggest strategies to help
you keep the drink down.
What to expect on test day
Here’s the step-by-step reality of a typical gestational diabetes screening day:
- Check-in. You’ll sign in at the lab or clinic. Staff will confirm which test you’re having (screening vs. diagnostic) and whether you’ve fasted if needed.
- Baseline measurements. For diagnostic tests, a fasting blood draw happens first. For the 1-hour screening, you may go straight to the drink.
-
The drink. You’re given a measured amount of glucose solution in a small bottle or cup. The flavor depends on the brand and clinic some people compare it to flat orange soda,
others to melted popsicles. You’ll usually be asked to finish it within 5 minutes. - The wait. You’ll wait in the lab or nearby while your body processes the sugar. Depending on the test, this can be 1 hour (screening) or up to 3 hours (OGTT).
- Repeated blood draws. A technician will draw blood at specific times. They’ll often use the same arm and may place a temporary bandage between draws.
- Heading home. Once the last blood sample is collected, you’re free to go, eat, and continue your day. Results are usually sent to your provider, who will contact you with next steps.
Common feelings during the test include:
- A bit of nausea from the sweetness, especially on an empty stomach
- Sleepiness or lightheadedness while you sit and wait
- A mild “sugar rush” feeling and then a crash as blood sugar rises and falls
If you feel very faint, extremely nauseated, or unwell, tell the staff immediately so they can help.
Understanding your gestational diabetes screening results
When your results come back, they usually fall into one of three categories:
1. Screen negative: no further testing needed (for now)
If your 1-hour glucose challenge test is below the cutoff value used by your clinic, you’ve “passed” the screening. In that case:
- You typically won’t need additional gestational diabetes testing unless new risk factors appear.
- Your routine prenatal care continues as usual.
It’s still a good idea to follow general healthy pregnancy habits: balanced meals, regular movement if cleared by your provider, and attending all prenatal appointments.
2. Screen positive: you need a diagnostic test
If your 1-hour value is above the cutoff, your provider will usually order the 3-hour OGTT (or a 75-gram OGTT if they use the one-step method). This can feel discouraging, but:
- A positive screening test does not automatically mean you have gestational diabetes.
- Many people with a mildly elevated screening result have normal diagnostic tests.
Think of the screening test like a metal detector at the airport: it beeps for anything that might be an issue, but more detailed scanning is needed to decide what’s really going on.
3. Diagnostic criteria met: you’re diagnosed with gestational diabetes
If your OGTT values meet or exceed the diagnostic thresholds used by your provider’s guidelines, you’ll receive a diagnosis of gestational diabetes. That can feel scary, but it also
means:
- Your care team now has clear information to help protect your health and your baby’s health.
- You’ll get specific guidance on nutrition, physical activity, and monitoring blood sugar.
- Many people with gestational diabetes have healthy pregnancies and healthy babies with the right care.
What happens if you’re diagnosed with gestational diabetes?
If you do have gestational diabetes, your care plan may include:
- Meeting with a diabetes educator or dietitian to learn how to balance carbs, protein, and fats in your meals.
- Checking your blood sugar at home using a meter, usually several times a day.
- Regular prenatal visits and extra monitoring of the baby’s growth and your health, especially in the third trimester.
- Medication if needed, such as insulin or other therapies, if diet and activity alone aren’t enough to keep blood sugar in range.
After delivery, gestational diabetes usually resolves. However, you’ll likely be retested 4–12 weeks postpartum and periodically after that, because having gestational diabetes raises
your lifetime risk of type 2 diabetes. The same lifestyle habits that help manage gestational diabetes (balanced meals, regular activity, healthy weight) can help lower that long-term risk.
Common questions about gestational diabetes screening
Is the glucose drink safe for my baby?
For most people, yes. The glucose drink is specifically designed and dosed for pregnancy tests. While it does deliver a quick sugar load, it’s brief and monitored, and the
benefits of detecting gestational diabetes early outweigh this short-term spike for the vast majority of patients. If you have severe nausea, a history of bariatric surgery,
or other special circumstances, talk with your provider about possible alternatives.
Can I refuse the test?
You always have the right to ask questions and discuss your options. However, professional groups strongly recommend routine gestational diabetes screening because many people with
gestational diabetes have no obvious symptoms and unmanaged high blood sugar can cause serious complications. If you have concerns about ingredients, timing, or
the testing method, bring them up with your provider so you can make an informed decision together.
Does failing the first test mean I did something wrong?
No. A positive screening test isn’t a judgment on your diet, willpower, or character. It mostly reflects how your body’s hormones and insulin are interacting during pregnancy.
Genetics, hormone levels, and underlying insulin sensitivity all play a role many of which you can’t control.
Can I “game” the test by eating a certain way?
It’s understandable to want to avoid extra testing, but deliberately trying to manipulate your blood sugar at the expense of accuracy can backfire. The whole point of
gestational diabetes screening is to protect you and your baby. The most helpful thing you can do is follow the instructions you’re given, show up as you are, and let your care team
interpret the results.
Real-life experiences: what gestational diabetes screening actually feels like
Medical brochures tend to say things like “you may experience mild discomfort,” which is technically true but not always the most helpful description. So what does all of
this actually feel like in real life? Here are some common patterns people report when they talk about their gestational diabetes screening experiences.
The 1-hour test: “like chugging liquid candy”
Many people describe the 1-hour glucose challenge test as “not fun, but manageable.” The drink itself is usually the star of the show. Some clinics offer different flavors
orange, fruit punch, lemon-lime. A lot of people find it tastes like very sweet flat soda, or melted popsicle juice. It’s not something you’d serve at a dinner party, but
it’s usually tolerable for those few minutes.
The next hour can feel surprisingly normal: you sit in the waiting room scrolling your phone, listening to a podcast, or answering emails. Some people feel a bit jittery or
wired shortly after the drink, followed by a sleepy wave as blood sugar rises and then starts to drop again. Others feel nothing special at all just slightly bored and
annoyed about parking.
One very common takeaway: bring something to do. Waiting in a lab chair with nothing but ceiling tiles to look at makes an hour feel much longer than it needs to be. A book, a show
queued up on your phone, or a favorite playlist can make the time pass more easily.
The 3-hour test: “a marathon of sitting still”
The longer diagnostic test feels more intense mainly because of the fasting and the number of blood draws. People often describe showing up feeling hungry, a little cranky, and very
ready for breakfast but knowing they have several hours to go before they can eat.
After the fasting blood draw, the stronger glucose drink can hit harder on an empty stomach. Some people feel nauseated or a bit dizzy as they sit and wait for the next
blood draws. Lab staff are used to this, so don’t be shy about telling them if you feel faint, overly sweaty, or like you might vomit. In many cases, they can recline the
chair, offer water if allowed, or check your blood pressure.
Emotionally, the long test can stir up anxiety: “What if I fail?” “Did I do something wrong?” “What will this mean for my baby?” It can help to remember that the test is
simply information. Whatever the outcome, having clear results allows your care team to support you more effectively.
A few practical tips people often wish they’d known ahead of time:
- Dress in layers. Labs can be cold, and you’ll be sitting for a while.
- Bring a support person if you can. Even just having someone to chat with can make the time go faster.
- Pack food for immediately after. A balanced snack with protein, fiber, and some carbs can help smooth out the post-test crash.
- Plan a low-key rest of the day. Many people feel tired afterward; this is a great time to schedule nothing but a nap and a comfy couch.
Getting the results: relief, frustration, and everything in between
Waiting for results can feel like its own emotional roller coaster. Some people refresh their patient portal every few hours. Others avoid looking until their provider calls.
It’s normal to feel nervous but remember that screening and diagnosis are not a reflection of your worth as a parent.
If your tests are normal, you may feel a big wave of relief and move on with the rest of your prenatal to-do list. If you’re diagnosed with gestational diabetes, it’s also
normal to feel upset, guilty, or overwhelmed at first. Many people find that once they meet with a diabetes educator and get a clear plan, that anxiety often shifts into a
sense of control: “Okay, here’s what I can do today.”
People who’ve been through it frequently say that the hardest part was the anticipation, not the test itself. The screening is just one piece of your pregnancy journey
important, yes, but also something you can get through with a bit of preparation, support, and information.
The bottom line
Gestational diabetes screening is a standard, evidence-based part of prenatal care that helps protect both you and your baby. It usually takes the form of a quick 1-hour glucose
challenge test around 24–28 weeks of pregnancy, with a longer oral glucose tolerance test if the first screening is elevated.
While the sugary drink, the waiting, and the blood draws aren’t exactly anyone’s favorite pregnancy memory, they provide crucial information. If your results are normal,
you’ve checked off an important box. If gestational diabetes is diagnosed, you and your care team can work together on a plan that supports a healthy pregnancy and lowers
risks now and in the future.
As always, this article is for general education only and is not a substitute for personal medical advice. Your own provider is the best person to explain which
gestational diabetes screening strategy they use, how to prepare, and what your specific numbers mean for you and your baby.
