By Jim Edwards, MD, FACOG. Board-Certified Maternal-Fetal Medicine Physician.

A gestational diabetes diagnosis lands differently for different people. For some, it is expected because of a known risk factor or family history. For others, it arrives as a surprise after an otherwise uneventful pregnancy. Either way, the weeks immediately after diagnosis are often the most overwhelming. New information, new equipment, new numbers, and new anxiety, all at once.

This article is for that period. Not the full arc of gestational diabetes management, but the first month: what you will be asked to do, why it matters, and what to expect as you find your footing.

What gestational diabetes is, and is not

Gestational diabetes mellitus (GDM) is a form of glucose intolerance that develops during pregnancy, typically diagnosed in the second or third trimester. It happens because pregnancy hormones, largely from the placenta, create a state of insulin resistance. Most people compensate by producing more insulin. GDM develops when the pancreas cannot keep up.

A few things worth saying clearly: a gestational diabetes diagnosis does not mean you did anything wrong. It is not caused by eating too much sugar. It is influenced by genetics, weight, age, ethnicity, and placental factors that are largely outside your control. With appropriate care, the large majority of people with GDM go on to have healthy pregnancies and healthy babies.

The diagnosis: what the numbers mean

Most U.S. obstetric practices use the two-step approach recommended by the American College of Obstetricians and Gynecologists (ACOG): a 50 gram nonfasting glucose challenge test at 24 to 28 weeks, followed by a 100 gram 3-hour oral glucose tolerance test (OGTT) if the screen is abnormal. ACOG's 2024 Clinical Practice Update reaffirms this approach and does not recommend routine GDM screening before 24 weeks. Some practices use a one-step 75 gram 2-hour OGTT instead, which is also acceptable.

For the standard 3-hour OGTT, two or more abnormal values establish the diagnosis using Carpenter-Coustan criteria:

If only one value is abnormal, your provider will guide you on next steps. Some practices treat a single abnormal value as impaired glucose tolerance and ask you to monitor closely without a formal GDM diagnosis.

The first two weeks

After diagnosis, you will typically be referred to a diabetes educator, a registered dietitian, or a combined perinatal diabetes program. This visit is the cornerstone of first-month management.

Nutrition counseling. The goal is not a punishing diet. It is carbohydrate distribution. Most people with GDM are asked to spread carbohydrates across three meals and two to three snacks, avoiding large carbohydrate loads at any one sitting. Breakfast is often the toughest meal, because cortisol peaks in the morning and drives higher post-breakfast readings. Your dietitian will give you targets based on your weight, activity level, and food preferences.

Home glucose monitoring. You will be given a glucometer and asked to check four times per day: a fasting value first thing in the morning before eating, and a value one or two hours after the start of each meal. Standard targets used by ACOG and SMFM:

Logging your numbers, either on paper or in a connected app, matters. Your care team uses trends, not isolated readings, to guide adjustments. A handful of high values during a stressful week is not the same picture as a steady upward drift.

Movement after meals. Walking after meals is one of the most effective and underrated tools in GDM. A 10 to 15 minute walk after eating can blunt the post-meal glucose spike meaningfully. This is not about exercise intensity. It is about timing. If walking after every meal is not feasible, even one or two postmeal walks per day helps.

What a useful blood sugar log looks like

A complete daily entry includes the time, the value, what you ate at the most recent meal, and any context that may explain a number. A 158 mg/dL reading taken at 11:30 a.m. after a granola bar at 10:00 is a different story than a 158 at the same time after a regular breakfast. Sleep, stress, illness, and how soon you ate after the glucose check are all worth noting. Your care team can read those notes and adjust the plan rather than guess.

When medication is added

For many people, food and movement are enough to keep values in target range throughout pregnancy. If readings remain elevated despite consistent effort, particularly fasting values, medication is the next step.

Insulin is the preferred first-line medication for GDM in current ACOG and SMFM guidance. It does not cross the placenta in meaningful amounts and has the longest safety record. Common regimens include bedtime long acting insulin for elevated fasting values and potentially mealtime rapid-acting insulin for postprandial spikes. Oral agents (metformin) are sometimes used and are effective. These cross the placenta to varying degrees, which is why insulin is preferred when possible.

Starting medication is not a failure of diet. Fasting hyperglycemia in particular is driven substantially by overnight liver glucose production, a process diet alone cannot fully control. Medication is a tool, not a verdict on your effort.

What to watch for in the first month

During the first month, your care team is watching two things: values consistently above target, which means the current plan needs adjustment, and values consistently below target, which can mean too much restriction or, if you are on insulin, a dose that needs to come down.

Call your provider if you notice any of the following:

The bigger picture

GDM resolves in most people after delivery, when the placental hormones driving insulin resistance are gone. A postpartum glucose tolerance test at 4 to 12 weeks after birth is recommended to confirm this and to screen for type 2 diabetes. The follow-up matters: up to half of people with a GDM history will develop type 2 diabetes within 10 years if risk factors are not addressed.

The first month is the steepest part of the learning curve. Most people find that by week 3 or 4 the monitoring feels routine and the food patterns become second nature. The skills you build now serve this pregnancy and your long-term health. A gestational diabetes diagnosis is, in many ways, an early signal and an early opportunity.

References

  1. American College of Obstetricians and Gynecologists. ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum. Obstet Gynecol. 2024;144(1):e10-e17. doi:10.1097/AOG.0000000000005612
  2. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol. 2018;131(2):e49-e64. PMID: 29370047.
  3. Society for Maternal-Fetal Medicine (SMFM). SMFM Statement: Pharmacological Treatment of Gestational Diabetes. Am J Obstet Gynecol. 2018;218(5):B2-B4. doi:10.1016/j.ajog.2018.01.041
  4. Crowther CA, Hiller JE, Moss JR, et al. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med. 2005;352(24):2477-2486. doi:10.1056/NEJMoa042973
  5. American Diabetes Association. Management of Diabetes in Pregnancy: Standards of Care in Diabetes 2025. Diabetes Care. 2025;48(Suppl 1):S306-S320.
This article is for informational purposes only and is based on evidence-based guidelines from organizations including the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM). It is not a substitute for personalized guidance from your healthcare provider. Every pregnancy is unique. If you have questions or concerns about your health or your baby's wellbeing, please reach out to your care team. In an emergency, call 911 or go to your nearest emergency department.