A 1-hour glucose test is a screening for gestational diabetes, typically done between 24 and 28 weeks of pregnancy. You drink a sweet liquid containing 50 grams of glucose, wait one hour, and then have your blood drawn to see how your body handled the sugar. It’s one of the most routine prenatal tests, and most people pass it without issue.
Why the Test Is Done
Gestational diabetes affects up to 10% of pregnant people. It develops when your body can’t produce enough insulin to keep up with the demands of pregnancy, causing blood sugar to rise higher than normal after eating. Left unmanaged, it can lead to complications like a larger-than-average baby, difficult delivery, and blood sugar problems for the newborn.
The tricky part is that gestational diabetes usually causes no obvious symptoms. You can feel perfectly fine and still have elevated blood sugar. That’s why screening is standard for nearly all pregnancies. If you have risk factors like obesity, a family history of diabetes, or a previous pregnancy with gestational diabetes, your provider may test you earlier than the typical 24-to-28-week window.
How the Test Works
The 1-hour glucose test is straightforward. You drink a liquid called glucola, which contains 50 grams of sugar dissolved in about 10 ounces of flavored liquid. Most clinics offer it in orange, lemon-lime, or fruit punch flavors. It tastes like a very sweet flat soda. You have about five minutes to finish it, and then you wait exactly one hour before a nurse draws your blood.
You do not need to fast beforehand. You can eat and drink normally before arriving, which is one of the things that makes this version of the test relatively easy. That said, some providers suggest avoiding a heavy, sugary meal right before the test, since loading up on carbohydrates could temporarily push your numbers higher.
During the one-hour wait, you’ll stay at the clinic or lab. Most people sit in the waiting room, read, or scroll their phone. You can’t eat, drink, or exercise during that hour, because any of those activities could affect your blood sugar reading.
What the Drink Feels Like
The glucose solution is intensely sweet, and that catches some people off guard. Drinking it on an otherwise normal stomach can cause nausea, and a smaller number of people feel lightheaded, jittery, or slightly queasy during the wait. These side effects are temporary and usually pass within an hour or two after the test. Drinking the solution cold tends to make it more tolerable. Some clinics refrigerate it ahead of time, but you can ask if yours doesn’t.
Understanding Your Results
Your results come back as a single blood sugar number measured in milligrams per deciliter (mg/dL). Here’s how to read it:
- Below 140 mg/dL: This is generally considered a normal result, and no further testing is needed.
- Between 140 and 189 mg/dL: Your blood sugar was higher than expected. Your provider will schedule a follow-up 3-hour glucose tolerance test to get a clearer picture.
- 190 mg/dL or higher: A result this high typically indicates gestational diabetes without needing the follow-up test.
It’s worth knowing that cutoff values can vary slightly between clinics and labs. Some providers use 130 mg/dL as their threshold for recommending the 3-hour test instead of 140. Your provider will tell you which standard they use.
What Happens If You Don’t Pass
A high result on the 1-hour test does not mean you have gestational diabetes. It means your body’s response to the sugar load needs a closer look. Roughly 15 to 25% of people who take the 1-hour screen get a result that triggers the follow-up, and most of them go on to pass the second test.
The follow-up is a 3-hour oral glucose tolerance test, and it’s more involved. Unlike the 1-hour screen, this one requires fasting for 8 to 14 hours beforehand. You’ll have your blood drawn when you arrive (a fasting baseline), then drink a higher-dose glucose solution containing 100 grams of sugar. Your blood is drawn again at the one-hour, two-hour, and three-hour marks. A diagnosis of gestational diabetes requires two or more of those four blood draws to come back above their respective cutoffs.
The 3-hour test is less comfortable than the screening. Fasting, drinking a larger sugar load, and sitting still for three hours with multiple blood draws can feel draining. Bring something to keep you occupied, and plan for a meal afterward.
Why Your Body Reacts This Way
During pregnancy, the placenta produces hormones that make your cells less responsive to insulin. This is a normal part of pregnancy and ensures your baby gets enough glucose for growth. In most cases, your pancreas compensates by producing more insulin to keep blood sugar in check.
When the pancreas can’t keep up with that increased demand, blood sugar starts creeping up, particularly after meals or, in this case, after drinking a concentrated sugar solution. The 1-hour test essentially gives your body a standardized sugar challenge and measures how well your insulin response handles it. A blood sugar level that stays elevated after one hour signals that your insulin production may not be matching the load.
If You’re Diagnosed With Gestational Diabetes
A confirmed diagnosis sounds alarming, but gestational diabetes is one of the most manageable pregnancy complications. For the majority of people, blood sugar can be controlled through dietary changes: eating smaller, more frequent meals, pairing carbohydrates with protein and fat, and monitoring blood sugar at home with a finger-stick meter. Regular walking or light exercise after meals also helps bring blood sugar down.
A smaller percentage of people need insulin or oral medication to keep their levels in range. Your provider will monitor you more closely for the rest of pregnancy, which usually means more frequent appointments and possibly additional ultrasounds to track your baby’s growth. After delivery, blood sugar almost always returns to normal. However, having gestational diabetes does increase your risk of developing type 2 diabetes later in life, so follow-up screening in the months and years after pregnancy is important.