Quick Facts
- Sample: Blood (serum or plasma)
- Fasting: Not required for initial screening; 8–14 hours for OGTT
- Turn-around: 1–2 business days. May take longer based on weather, holiday or lab delays.
Benefits
- Early detection prevents serious pregnancy complications for you and baby
- Convenient screening without requiring a doctor's visit or appointment
- Fast results available within 1-2 business days for timely intervention
- Evidence-based testing following ACOG recommendations for accurate diagnosis
- Cost-effective alternative to traditional clinic-based testing
- Privacy and convenience with secure online ordering and results
Who Is This Test For?
- All pregnant women between 24-28 weeks of pregnancy
- High-risk individuals with family history of diabetes or obesity
- Women with previous gestational diabetes in prior pregnancies
- Those seeking convenient prenatal screening outside traditional healthcare settings
- Individuals wanting early detection to prevent pregnancy complications
How It Works – Just 3 Steps
- Order online and visit a nearby lab location or request home collection
- Drink glucose solution and provide blood samples at specified intervals
- Receive secure results within 1-2 business days
FAQ
What happens if I test positive for gestational diabetes? Your healthcare provider will recommend dietary changes, blood sugar monitoring, and possibly medication to manage the condition throughout pregnancy.
Is this test safe during pregnancy? Yes, the glucose challenge test is completely safe and routinely recommended by the American College of Obstetricians and Gynecologists (ACOG 2018).
Can I eat before the initial screening test? No fasting is required for the one-hour glucose challenge test, but avoid eating unusually large amounts of sugar beforehand.
What if I can't keep the glucose drink down? Contact the lab immediately, as the test timing is critical. You may need to reschedule or discuss alternative testing methods with your provider.
How accurate is this test? The glucose challenge test correctly identifies about 80% of women with gestational diabetes, with follow-up testing confirming the diagnosis (NIDDK 2023).
More Details
What is the purpose of this test?
This test detects gestational diabetes mellitus (GDM), a temporary form of diabetes that develops during pregnancy when your body cannot produce enough insulin to meet increased needs. The test measures how efficiently your body processes sugar by monitoring blood glucose levels after consuming a standardized glucose solution (Mayo Clinic 2022).
Gestational diabetes affects approximately 6-9% of pregnancies in the United States and can lead to serious complications if left undetected, including preeclampsia, cesarean delivery, and babies born with breathing difficulties or low blood sugar (CDC 2023).
Who would benefit from this test?
All pregnant women should be screened for gestational diabetes, but certain individuals are at higher risk and may benefit from earlier or more frequent testing. Risk factors include being overweight before pregnancy, having a family history of diabetes, being over age 25, or having had gestational diabetes in a previous pregnancy (JAMA Network 2021).
Women from certain ethnic backgrounds, including Hispanic, African American, Native American, and Asian populations, also have increased risk and should prioritize this screening. Early detection allows for timely intervention through diet modification, exercise, and medication if necessary.
When should I order this test?
The standard recommendation is to test between 24-28 weeks of pregnancy when insulin resistance naturally increases. However, women with high risk factors may need testing as early as the first trimester and again later in pregnancy (NIDDK 2023).
If you have multiple risk factors or symptoms like excessive thirst, frequent urination, or unusual fatigue, discuss earlier testing with your healthcare provider. Some recent research suggests earlier testing may benefit high-risk women (Lancet 2024).
How do I interpret the results?
Results depend on which test you receive. The initial one-hour glucose challenge test uses a single threshold, while the three-hour oral glucose tolerance test (OGTT) requires multiple elevated readings for diagnosis.
1-hour screening
- Threshold: ≥140 mg/dL
- What it means: Possible gestational diabetes
- Typical action: Follow-up with 3-hour OGTT
3-hour OGTT (fasting)
- Threshold: ≥95 mg/dL
- What it means: Elevated baseline glucose
- Typical action: Count toward diagnosis
3-hour OGTT (1-hour)
- Threshold: ≥180 mg/dL
- What it means: Impaired glucose processing
- Typical action: Count toward diagnosis
3-hour OGTT (2-hour)
- Threshold: ≥155 mg/dL
- What it means: Sustained elevation
- Typical action: Count toward diagnosis
3-hour OGTT (3-hour)
- Threshold: ≥140 mg/dL
- What it means: Prolonged elevation
- Typical action: Count toward diagnosis
Two or more elevated values on the 3-hour OGTT confirm gestational diabetes diagnosis (Labcorp 2023).
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
For the initial one-hour glucose challenge test, no special preparation is needed. Eat normally but avoid consuming unusually large amounts of sugar immediately before testing. You'll drink a glucose solution at the lab and have blood drawn exactly one hour later.
If you need the three-hour OGTT follow-up test, more preparation is required. Eat an unrestricted diet with at least 150 grams of carbohydrates daily for three days before testing. Fast for 8-14 hours before the appointment, drinking only water. Avoid medications that affect blood sugar for three days prior, unless medically necessary (Labcorp 2023).
How often should I get tested?
- Standard risk pregnancy: Once between 24–28 weeks
- High risk factors: First trimester and 24–28 weeks
- Previous gestational diabetes: Early pregnancy and 24–28 weeks
- Abnormal early screen: Repeat at 24–28 weeks if initially normal
- Post-pregnancy follow-up: 6–12 weeks after delivery
Why early detection matters
Undetected gestational diabetes significantly increases risks for both mother and baby. Maternal complications include a doubled risk of preeclampsia, increased likelihood of cesarean delivery, and higher chance of developing type 2 diabetes later in life. For babies, risks include macrosomia (excessive birth weight), breathing difficulties, and low blood sugar at birth.
Early detection and management through diet, exercise, and medication when needed can reduce these complications by up to 50%. Women who receive proper treatment have pregnancy outcomes similar to those without gestational diabetes (JAMA Network 2021).
Related tests you may consider
Hemoglobin A1c Blood Test calculates the average blood glucose levels over 2-3 months, making it an ideal diagnostic tool for diabetes management.
Glucose Serum Testchecks how much sugar is in your blood to see if your body is handling it well, which can help doctors find or manage conditions like diabetes or low blood sugar.
Insulin Fasting Blood Testmeasures how much insulin is in your blood after not eating, helping doctors check for problems like diabetes and insulin resistance.
