Glucose Gestational Screen 50g (135 Cutoff) Biomarker Testing
It screens for gestational diabetes risk after a 50g glucose drink, with results interpreted using a 135 mg/dL cutoff—order through Vitals Vault at Quest.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
This test is the common first step for screening gestational diabetes during pregnancy. You drink a 50-gram glucose solution, and your blood glucose is measured one hour later.
The “135 cutoff” refers to one of the thresholds many clinics use to decide whether your screening result is considered positive and should be followed by a longer diagnostic test. A positive screen does not mean you have gestational diabetes, but it does mean you need follow-up.
Because labs and clinics can use different cutoffs (often 130, 135, or 140 mg/dL), it helps to interpret your number in the context of your pregnancy week, your risk factors, and your clinician’s protocol.
Do I need a Glucose Gestational Screen 50g 135 Cutoff test?
You may need this test if you are pregnant and your clinician recommends routine screening for gestational diabetes, most commonly between 24 and 28 weeks. Some people are screened earlier if they have higher risk, such as a prior pregnancy with gestational diabetes, a history of delivering a large baby, polycystic ovary syndrome (PCOS), prediabetes, or a strong family history of type 2 diabetes.
You might also be asked to screen if an ultrasound suggests the baby is measuring large for gestational age, if you have excess amniotic fluid (polyhydramnios), or if you have persistent glucose in the urine on prenatal visits. Symptoms are not a reliable guide, because gestational diabetes can be present even when you feel well.
This is a screening test, not a diagnosis. Your result is meant to guide next steps with your prenatal clinician, usually deciding whether you should complete a 3-hour oral glucose tolerance test (OGTT) for confirmation.
This screening glucose measurement is performed in a CLIA-certified laboratory; results should be interpreted with your prenatal clinician and are not a standalone diagnosis of gestational diabetes.
Lab testing
Order the 50g gestational glucose screen and test at a Quest location.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you want a clear, trackable record of your gestational diabetes screening, you can order the Glucose Gestational Screen 50g (135 cutoff) through Vitals Vault and complete the blood draw at a Quest location.
After your results post, PocketMD can help you understand what a “positive screen” means, what follow-up testing is typically recommended, and what questions to bring to your prenatal visit. This is especially useful if you are comparing different cutoffs (130 vs 135 vs 140) or you are unsure whether you were fasting.
If you need to retest or your clinician wants confirmatory testing, you can use the same Vitals Vault account to keep your pregnancy glucose results organized over time and to add companion labs when broader metabolic context is needed.
- Order online and test at a Quest location
- Clear results view with optional PocketMD guidance
- Easy re-order for follow-up testing if your screen is positive
Key benefits of Glucose Gestational Screen 50g (135 cutoff) testing
- Screens for gestational diabetes risk with a simple 1-hour blood draw after a 50g glucose drink.
- Helps identify people who need confirmatory testing (3-hour OGTT) before complications develop.
- Supports earlier nutrition and activity planning when glucose handling looks borderline in pregnancy.
- Provides an objective number when symptoms are absent or nonspecific.
- Clarifies whether a higher-risk pregnancy warrants closer glucose monitoring.
- Creates a baseline you can compare with later pregnancy labs or postpartum glucose testing.
- Pairs well with PocketMD guidance so you know what “positive screen” means and what to do next.
What is Glucose Gestational Screen 50g (135 cutoff)?
The Glucose Gestational Screen 50g is a pregnancy screening test that measures your blood glucose level one hour after you drink a solution containing 50 grams of glucose. It is often called the “1-hour glucose challenge test” (GCT).
Pregnancy hormones naturally increase insulin resistance, especially in the second and third trimesters. Most people compensate by making more insulin, but some cannot keep up. When that happens, blood glucose rises more than expected after a glucose load. This screening test looks for that pattern.
The “135 cutoff” is a decision threshold used by many practices. If your 1-hour value is at or above 135 mg/dL, the screen is typically considered positive and you are usually advised to complete a diagnostic oral glucose tolerance test (often a 100g, 3-hour OGTT). Some clinics use 130 or 140 mg/dL instead, so your next step should follow your clinician’s protocol.
Screening vs diagnostic testing
A screening test is designed to catch most people who might have the condition, even if that means some false positives. A diagnostic OGTT is longer and uses multiple blood draws to confirm whether you meet criteria for gestational diabetes.
When it is usually done
Routine screening is most often performed at 24–28 weeks because insulin resistance tends to rise as pregnancy progresses. Earlier screening may be recommended if you have risk factors or if earlier labs suggest elevated glucose.
What do my Glucose Gestational Screen 50g (135 cutoff) results mean?
Lower 1-hour glucose on the 50g screen
A lower result generally means your body cleared the glucose load efficiently at the time of testing. In most cases, that is reassuring and you will not need additional glucose testing unless your clinician has other concerns. Very low values are uncommon and are usually not harmful, but if you felt shaky, sweaty, or faint after the drink, tell your clinician because reactive symptoms can matter for your comfort and nutrition planning. Your overall pregnancy context still matters, including your weight gain pattern and ultrasound findings.
In-range (negative screen) with a 135 mg/dL cutoff
If your 1-hour value is below 135 mg/dL, the screen is typically considered negative under a 135 cutoff protocol. That usually means you do not need the 3-hour OGTT. Keep in mind that different practices use different cutoffs, so a value like 134 mg/dL may be “negative” in one clinic and “positive” in another. If you are close to the threshold, your clinician may still consider your risk factors and may repeat testing or monitor more closely.
High (positive screen) at or above 135 mg/dL
A result at or above 135 mg/dL is commonly treated as a positive screen, meaning you have a higher chance of gestational diabetes and should usually complete confirmatory testing. This does not diagnose gestational diabetes by itself, because many people with a positive screen have a normal 3-hour OGTT. The next step is typically scheduling the diagnostic test and, in some cases, starting basic nutrition steps while you wait. If your value is markedly elevated, your clinician may move faster with follow-up or consider additional monitoring.
Factors that can influence your screening glucose result
Timing matters: the blood draw is intended to be exactly one hour after finishing the glucose drink, and delays can shift the number. Recent diet, illness, poor sleep, stress, and reduced activity can raise glucose temporarily. Certain medications (for example, corticosteroids) can increase glucose, and nausea or vomiting during the test can make results harder to interpret. Lab methods are standardized, but clinic protocols differ, including whether you were asked to fast, what cutoff is used, and whether you were screened earlier than 24–28 weeks.
What’s included
- Glucose, Gestational Screen (50G)-135 Cutoff
Frequently Asked Questions
Do I need to fast for the 50g glucose gestational screen?
Many clinics do not require fasting for the 50g screening test, but protocols vary. Follow the instructions you were given for your appointment, because eating right before the drink can affect your result and how your clinician interprets it.
What does the “135 cutoff” mean on my result?
It means the lab or ordering protocol uses 135 mg/dL as the threshold for a positive screen. If your 1-hour glucose is 135 mg/dL or higher, the screen is typically flagged as positive and you are usually advised to do a diagnostic 3-hour OGTT.
If my screen is positive, do I definitely have gestational diabetes?
No. The 50g test is a screening tool, so it is designed to be sensitive. Many people who screen positive have a normal diagnostic OGTT and do not meet criteria for gestational diabetes.
What happens after a positive 1-hour glucose challenge test?
The usual next step is a diagnostic oral glucose tolerance test, often a 100g, 3-hour OGTT with multiple blood draws. Your clinician may also recommend practical steps while you wait, such as balanced meals with protein and fiber, and regular movement if it is safe in your pregnancy.
Why do some clinics use 130, 135, or 140 mg/dL as the cutoff?
Different cutoffs balance sensitivity and specificity differently. A lower cutoff (like 130) catches more potential cases but increases false positives, while a higher cutoff (like 140) reduces false positives but may miss some cases. Your clinic chooses a protocol based on guidelines, population risk, and practice preference.
Can I fail the 1-hour test and pass the 3-hour test?
Yes, and it is common. The 1-hour screen identifies people who may need more detailed testing, while the 3-hour OGTT determines whether your glucose values meet diagnostic thresholds over time.
What if I vomit during the glucose drink test?
If you vomit, the test may not be valid because the glucose load and timing are disrupted. Contact your clinician or the testing site; they may reschedule the screen or choose a different approach based on your situation.