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If you’re approaching the end of your second trimester, you’ve probably heard about the glucose test in pregnancy—the gestational diabetes screening that typically happens between 24 and 28 weeks. For many expecting parents, this test can bring up a lot of questions:
- What exactly is gestational diabetes?
- Why do I need to be tested?
- What happens if I fail the screening?
- Are there alternatives to the glucose drink?
- How will a diagnosis affect my pregnancy and birth plans?
Let’s break down everything you need to know about gestational diabetes, including how it develops, how it’s diagnosed, potential risks, and what happens if you receive a diagnosis.
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What Is Gestational Diabetes?
Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy in someone who did not previously have diabetes.
During pregnancy, hormonal changes naturally increase insulin resistance. This is actually a normal and important adaptation because it helps ensure that more glucose remains available in the bloodstream to support your growing baby.
Most pregnant bodies compensate for this increased insulin resistance by producing more insulin. However, when the pancreas cannot keep up with the increased demand, blood glucose levels rise above normal levels, resulting in gestational diabetes.
Understanding Insulin and Glucose
To understand gestational diabetes, it helps to understand the relationship between insulin and glucose.
Glucose is the body’s primary source of quick energy and comes from the foods we eat.
Insulin is a hormone produced by the pancreas that acts like a key, allowing glucose to move from the bloodstream into the body’s cells where it can be used for energy.
When insulin isn’t working effectively or the body becomes resistant to insulin, glucose remains in the bloodstream instead of entering the cells. This leads to elevated blood sugar levels, known as hyperglycemia.
During pregnancy, some insulin resistance is expected. Gestational diabetes occurs when that normal pregnancy-related insulin resistance exceeds the body’s ability to compensate.
How Common Is Gestational Diabetes?
Gestational diabetes affects approximately 2% to 10% of pregnancies.
While many people have identifiable risk factors, it’s important to remember that gestational diabetes can develop in anyone—even those who exercise regularly, maintain a balanced diet, and have no prior health concerns.
A diagnosis is not a reflection of something you did wrong. Pregnancy hormones play a major role in its development.
Risk Factors for Gestational Diabetes
Several factors can increase the likelihood of developing gestational diabetes, including:
Previous Gestational Diabetes
If you’ve had gestational diabetes in a prior pregnancy, your risk of developing it again increases significantly.
Higher Body Mass Index (BMI)
Individuals with a higher BMI may have increased baseline insulin resistance, making it harder for the body to compensate during pregnancy.
Physical Inactivity
Regular movement helps improve insulin sensitivity, so a sedentary lifestyle may increase risk.
Medical Conditions
Certain conditions are associated with increased insulin resistance, including:
- Polycystic Ovary Syndrome (PCOS)
- Chronic hypertension
- Cardiovascular disease
Previous Large Baby
Having previously delivered a baby weighing more than 9 pounds can increase your risk.
Ethnicity
Certain populations have higher rates of gestational diabetes, including:
- Asian
- Pacific Islander
- African American
- Hispanic
- Native American
Even without any of these risk factors, gestational diabetes can still occur.
When Is the Glucose Test in Pregnancy Performed?
Gestational diabetes screening is typically performed between 24 and 28 weeks of pregnancy, which corresponds to the end of the second trimester and beginning of the third trimester.
This timing aligns with when pregnancy hormones become most likely to affect insulin sensitivity.
The One-Hour Glucose Screening Test
In the United States, the most common screening method is the one-hour oral glucose tolerance test.
What Happens During the Test?
You will:
- Drink a beverage containing 50 grams of glucose.
- Consume the drink within five minutes.
- Have your blood drawn one hour later.
The purpose of this test is to evaluate how effectively your body responds to a sudden increase in glucose.
Do You Need to Fast?
A common misconception is that you must fast before the one-hour test.
You do not need to fast before the one-hour glucose screening.
You can eat normally unless your provider gives you specific instructions.
What If You Fail the Screening?
The one-hour test is a screening tool, not a diagnostic test.
Depending on your provider’s guidelines, a blood sugar value above approximately 135–145 mg/dL may be considered abnormal.
If your results exceed the cutoff, you’ll likely be scheduled for a three-hour glucose tolerance test for further evaluation.
The Three-Hour Glucose Tolerance Test
The three-hour oral glucose tolerance test is considered the diagnostic test for gestational diabetes.
What Happens During the Three-Hour Test?
Unlike the one-hour screening, this test requires fasting.
Your provider will:
- Check a fasting blood sugar level.
- Have you drink a solution containing 100 grams of glucose.
- Draw blood at one hour, two hours, and three hours after drinking.
A diagnosis of gestational diabetes is generally made when two or more values exceed established thresholds.
Why Is the Oral Glucose Tolerance Test Considered the Gold Standard?
The oral glucose tolerance test is considered the gold standard because it is:
- Standardized
- Highly researched
- Easily replicated
- Proven to improve pregnancy outcomes
Research has shown that identifying and managing gestational diabetes can reduce complications such as:
- Shoulder dystocia
- Cesarean birth
- Large-for-gestational-age babies (macrosomia)
- Neonatal hypoglycemia
Alternatives to the Traditional Glucose Drink
After drinking the glucose solution, many pregnant individuals report feeling:
- Nauseated
- Lightheaded
- Tingly
- Dizzy
- Generally unwell
Because of this, some people seek alternative testing options.
At-Home Blood Sugar Monitoring
One alternative is self-monitoring blood glucose levels at home.
This may involve checking blood sugar:
- Fasting each morning
- One or two hours after meals
Some providers recommend monitoring for two weeks, while others may continue monitoring throughout pregnancy.
Continuous Glucose Monitoring (CGM)
Some individuals use a continuous glucose monitor (CGM), which tracks blood sugar levels throughout the day without repeated finger sticks.
Limitations of Alternative Testing
While these methods provide valuable information about real-life blood sugar patterns, they are not currently considered equivalent to the oral glucose tolerance test.
Because diet and eating habits vary significantly between individuals, these methods are more difficult to standardize and study.
For now, the oral glucose tolerance test remains the recommended screening tool.
Alternative Glucose Drinks
If you’re concerned about the ingredients in the traditional Glucola drink, discuss alternatives with your provider.
Some options may include:
Glucola
The traditional glucose beverage used in most clinics.
The Fresh Test
A lemonade-flavored alternative containing the same amount of glucose and approved for diabetes screening.
Many individuals report finding it easier to tolerate than traditional Glucola.
Other Provider-Specific Options
Some practices may use:
- Certain fruit juices
- Specific meals
- Jelly beans
However, these alternatives are less standardized and may not be supported by the same level of research.
Why Does Gestational Diabetes Matter?
The primary reason for screening is that uncontrolled gestational diabetes can increase risks for both parent and baby.
The good news is that identifying gestational diabetes allows providers to manage it effectively and significantly reduce these risks.
Risks for the Pregnant Person
Increased Risk of Cesarean Birth
Elevated blood sugar levels can contribute to larger babies, which may increase the likelihood of cesarean delivery.
Increased Risk of Shoulder Dystocia
Excess glucose crosses the placenta and stimulates increased insulin production in the baby.
Insulin acts as a growth hormone, often resulting in larger shoulder measurements and increased risk of shoulder dystocia during birth.
Hypertensive Disorders
Gestational diabetes is associated with an increased risk of:
- Gestational hypertension
- Preeclampsia
Future Type 2 Diabetes
Individuals diagnosed with gestational diabetes have a higher risk of developing Type 2 diabetes later in life.
Risks for the Baby
Larger Birth Weight
Babies exposed to elevated maternal blood sugar levels may grow larger than average.
Birth Complications
A larger baby may face increased risks of:
- Shoulder dystocia
- Birth injuries
- Nerve injuries
- Cesarean birth
Low Blood Sugar After Birth
After delivery, the baby’s glucose supply from the placenta stops immediately.
However, the baby’s insulin levels may remain elevated for a period of time, increasing the risk of neonatal hypoglycemia.
Because of this, babies born to mothers with gestational diabetes often have their blood sugar monitored after birth.
Long-Term Health Risks
Research suggests increased risks later in life for:
- Higher BMI
- Insulin resistance
- Type 2 diabetes
Controlled vs. Uncontrolled Gestational Diabetes
An important distinction is that many of these risks are most strongly associated with uncontrolled gestational diabetes.
When blood sugar levels remain well-managed, pregnancy outcomes are often very similar to those without gestational diabetes.
This is exactly why screening and treatment are so valuable.
Types of Gestational Diabetes
GDM-A1: Diet-Controlled Gestational Diabetes
This type is managed through:
- Dietary modifications
- Exercise
- Lifestyle changes
Pregnancy management often remains relatively unchanged aside from blood sugar monitoring.
Delivery is generally recommended by 40 weeks and 6 days.
Additional fetal testing is not routinely required when blood sugars remain well controlled.
GDM-A2: Medication-Controlled Gestational Diabetes
This type requires medication such as:
- Insulin
- Metformin
- Glyburide
With medication-controlled gestational diabetes, providers typically recommend:
- Antenatal testing beginning around 32 weeks
- Additional ultrasounds
- Delivery around 39 weeks
In some situations, earlier delivery may be recommended based on blood sugar control and fetal well-being.
Managing Gestational Diabetes
Management usually includes:
- Monitoring blood sugar levels
- Eating balanced meals
- Prioritizing protein and fiber
- Staying physically active
- Following provider recommendations regarding medications if needed
The goal is not perfection—it is maintaining blood sugar levels within a target range to support healthy outcomes for both parent and baby.
Final Thoughts
Gestational diabetes can feel overwhelming when you first hear the diagnosis, but it is a common and highly manageable condition.
Screening allows healthcare providers to identify concerns early, monitor blood sugar levels, and reduce risks throughout pregnancy and birth.
Whether you choose the traditional glucose screening or discuss alternative monitoring options with your provider, the most important thing is finding an approach that helps you feel informed, supported, and confident in your care.
A diagnosis of gestational diabetes does not mean you have failed. It simply means your pregnancy requires a little more monitoring and support—and with proper management, most individuals go on to have healthy pregnancies, healthy births, and healthy babies.
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