Gestational diabetes rarely causes noticeable symptoms, so most people don’t know they have it until routine screening picks it up between 24 and 28 weeks of pregnancy. That’s why blood sugar testing during pregnancy is standard, not optional. If you’re wondering whether you might have gestational diabetes, here’s what to watch for, how testing works, and what the results mean.
Why Symptoms Alone Won’t Tell You
Unlike type 1 or type 2 diabetes, gestational diabetes almost never announces itself with obvious warning signs. Being thirstier than usual and urinating more frequently are possible symptoms, but those overlap so heavily with normal pregnancy that they’re easy to dismiss. Most people with gestational diabetes feel perfectly fine, which is exactly why screening matters so much.
The condition develops because of hormonal shifts in the second half of pregnancy. As the placenta grows, it produces increasing amounts of progesterone, cortisol, and placental growth hormone. These hormones make your body’s cells less responsive to insulin, the hormone that moves sugar from your blood into your cells. For most pregnant people, the pancreas compensates by producing more insulin. When it can’t keep up, blood sugar rises and gestational diabetes develops.
Who Gets Screened Early
Standard screening happens between 24 and 28 weeks, but your provider may test you at your very first prenatal visit if you carry certain risk factors. These include obesity, being over 35, a history of gestational diabetes in a previous pregnancy, a family history of type 2 diabetes, or having delivered a large baby before. Belonging to a racial or ethnic group at higher risk for type 2 diabetes (Hispanic, Native American, South Asian, East Asian, or Pacific Islander descent) also puts you in the earlier screening category.
Early testing doesn’t use a different method. It simply moves the standard glucose tests to the first trimester so that if blood sugar is already elevated, management can start sooner rather than waiting until the third trimester.
The Initial Screening Test
The most common approach in the U.S. is a two-step process. Step one is the glucose challenge test, sometimes called the one-hour test. You drink a sugary liquid containing 50 grams of glucose, and your blood is drawn one hour later. You don’t need to fast beforehand, so you can eat and drink normally before the appointment.
If your blood sugar at the one-hour mark comes back at 130 or 140 mg/dL or higher (the exact cutoff depends on your provider’s practice), you move on to the second, more definitive test. A result above the threshold doesn’t mean you have gestational diabetes. It means your body needs a closer look.
The Diagnostic Test
The follow-up is a three-hour glucose tolerance test that requires overnight fasting. At the appointment, your fasting blood sugar is drawn first. Then you drink a larger glucose solution containing 100 grams. Your blood is drawn three more times: at one hour, two hours, and three hours after the drink.
Gestational diabetes is diagnosed if two or more of these readings come back above the thresholds:
- Fasting: 95 mg/dL or higher
- One hour: 180 mg/dL or higher
- Two hours: 155 mg/dL or higher
- Three hours: 140 mg/dL or higher
If only one value is elevated, you typically won’t receive a diagnosis, though your provider may recommend dietary changes and closer monitoring for the rest of your pregnancy.
The One-Step Alternative
Some providers use a single, slightly different test instead. This version uses 75 grams of glucose and takes two hours rather than three. Blood is drawn fasting, at one hour, and at two hours. The thresholds are slightly different: fasting of 92 mg/dL, one-hour of 180 mg/dL, and two-hour of 153 mg/dL. With this approach, only one elevated value is needed for a diagnosis. Your provider will tell you which method they use.
What the Test Feels Like
The glucose drink is very sweet, often compared to flat orange soda or a melted popsicle. Some people feel queasy after drinking it, especially during the longer three-hour test when you’re fasting. You’ll need to stay at the lab or clinic for the full duration so your blood can be drawn at precise intervals. Bring something to read or watch. You can’t eat during the test, but water is usually fine.
For the three-hour version, plan to eat a good meal the night before and arrange your morning around the appointment. Most people feel a bit drained afterward, so having a snack ready for when you leave is a good idea.
What Happens After a Diagnosis
If your numbers confirm gestational diabetes, the first step is almost always dietary. You’ll work with your care team (often including a dietitian) to adjust what and when you eat, focusing on balancing carbohydrates with protein and fat to keep blood sugar steady throughout the day. You’ll also start checking your blood sugar at home, typically four times a day: once fasting in the morning and once after each meal.
Many people manage gestational diabetes with diet and activity changes alone. Regular movement, even a 15-to-20-minute walk after meals, can meaningfully lower post-meal blood sugar. When lifestyle changes aren’t enough, insulin or another medication may be added. Your provider will increase monitoring of your baby’s growth in the third trimester, since elevated blood sugar can cause the baby to grow larger than average.
Gestational diabetes typically resolves after delivery. Your blood sugar will be checked again in the postpartum period to confirm it has returned to normal. However, having gestational diabetes does raise your lifetime risk of developing type 2 diabetes, so follow-up testing every one to three years is recommended going forward.