The glucose test during pregnancy is a routine blood test that checks how well your body processes sugar. It screens for gestational diabetes, a condition where blood sugar levels rise too high during pregnancy. Most pregnant people take this test between 24 and 28 weeks, though your provider may recommend it earlier if you have certain risk factors.
Why the Test Matters
During pregnancy, your body naturally becomes more resistant to insulin, the hormone that moves sugar from your blood into your cells. For most people, the body compensates by producing more insulin. But when it can’t keep up, blood sugar stays elevated, and that’s gestational diabetes.
Unmanaged high blood sugar during pregnancy increases the risk of several complications. Babies are more likely to grow too large, which raises the chance of a cesarean delivery. They also face a higher risk of developing obesity or type 2 diabetes later in life. For the mother, gestational diabetes increases the risk of preeclampsia and preterm birth. The glucose test catches the condition early enough to manage it effectively.
How the 1-Hour Screening Works
The first step is usually the glucose challenge test, sometimes called the 1-hour test. You drink a sweet liquid containing a measured amount of glucose, then have your blood drawn one hour later. You don’t need to fast beforehand, and you can eat normally the day of the test. The whole process takes a little over an hour.
If your blood sugar comes back below 140 mg/dL, your result is normal and no further testing is needed. Some clinics use a lower cutoff of 130 mg/dL. A result between 140 and 190 mg/dL means you’ll need the longer follow-up test. If your blood sugar reads 200 mg/dL or higher, that may indicate type 2 diabetes rather than gestational diabetes, and your provider will discuss next steps.
An elevated result on the 1-hour test doesn’t mean you have gestational diabetes. Many people who “fail” the screening go on to pass the diagnostic test. Think of this first test as a broad net designed to catch anyone who might need closer evaluation.
The 3-Hour Diagnostic Test
If your screening result is elevated, you’ll be scheduled for the oral glucose tolerance test, commonly called the 3-hour test. This one requires fasting for at least eight hours beforehand, so most people schedule it first thing in the morning.
When you arrive, your blood is drawn to measure your fasting blood sugar. Then you drink a glucose solution containing 100 grams of sugar (twice the amount in the screening test). Your blood is drawn again at the one-hour, two-hour, and three-hour marks. You’ll need to stay at the clinic or lab for the full duration.
A gestational diabetes diagnosis requires elevated readings at two or more of the four blood draws (fasting, one hour, two hours, three hours). If only one value is high, you typically won’t receive a diagnosis, though your provider may recommend monitoring your diet more closely.
What the Glucose Drink Feels Like
The glucose solution is essentially flat, very sweet soda. Most people describe it as intensely sugary, similar to melted popsicle or overly sweet orange or lemon-lime drink. You usually need to finish it within five minutes.
Some people feel nauseous, lightheaded, or jittery afterward. These reactions are normal and typically pass within a couple of hours. For the 3-hour test, bringing something to read or do helps pass the time since you can’t eat until it’s over. Having a snack ready for after the final blood draw is a good idea.
If you’re concerned about the standard glucose drink, ask your provider about alternatives. Many facilities carry dye-free, clear versions. There are also products like The Fresh Test, which uses organic glucose with minimal ingredients and works the same way for lab purposes.
What Happens After a Diagnosis
If you’re diagnosed with gestational diabetes, the first line of treatment is dietary changes and exercise. A typical approach focuses on increasing fiber, vegetables, lean protein, and whole grains while cutting back on refined carbohydrates like white bread, white rice, and sweets. Moderate exercise for about 30 minutes most days, such as walking, cycling, or swimming, also helps your body use insulin more effectively.
You’ll likely be asked to check your blood sugar four or more times a day: first thing in the morning and after meals. This tells you and your provider how specific foods affect your levels in real time. Many people manage gestational diabetes through diet and movement alone. When those changes aren’t enough to keep blood sugar in a healthy range, insulin injections or oral medication may be added.
Your provider will also monitor your baby more closely with additional ultrasounds throughout the rest of your pregnancy. After delivery, your blood sugar is checked again, and then rechecked at 6 to 12 weeks postpartum to confirm it has returned to normal. Even if it does, you’ll need diabetes screening at least every three years going forward, since having gestational diabetes increases your long-term risk of developing type 2 diabetes.