Diabetes Medications During Pregnancy: Insulin vs. Oral Options Explained

Managing Diabetes During Pregnancy: What You Need to Know

If you’re pregnant and have diabetes-whether it was there before pregnancy or developed during it-you’re probably wondering what medications are safe. The truth is, your blood sugar control isn’t just about how you feel. It directly affects your baby’s health. High blood sugar during pregnancy can lead to big babies, early delivery, breathing problems at birth, or even long-term metabolic issues for your child. The goal is simple: keep glucose levels tight, without putting your baby at risk.

Why Insulin Is Still the Gold Standard

Insulin is the most trusted medication for diabetes in pregnancy. It doesn’t cross the placenta, so it doesn’t reach the baby. That’s why it’s been the go-to for decades. Whether you have type 1, type 2, or gestational diabetes that won’t respond to diet and exercise alone, insulin is the first-line treatment recommended by the Endocrine Society (2023) and the American College of Obstetricians and Gynecologists (ACOG).

Not all insulins are the same. Rapid-acting analogs like insulin lispro and insulin aspart are preferred over regular insulin because they work faster after meals and lower the risk of low blood sugar later. Long-acting insulin options are trickier. Insulin detemir and insulin glargine have been studied in hundreds of pregnant women and appear as safe as the older NPH insulin. But newer options like insulin degludec and insulin glulisine? There’s not enough data. Experts advise against using them during pregnancy.

Many women use insulin pens or multiple daily injections. But if you’re already on an insulin pump before pregnancy, you can usually keep using it. Studies show no major difference in outcomes between pump therapy and injections, though some women find pumps easier to manage with changing insulin needs as pregnancy progresses.

Oral Medications: Metformin and the Gray Area

Metformin is the only oral medication with meaningful data in pregnancy. It’s not approved by the FDA for gestational diabetes, but it’s used off-label-and often effectively. In studies, women taking metformin had fewer large babies, less preeclampsia, and lower rates of NICU admissions compared to those on insulin.

But here’s the catch: about half of women on metformin eventually need insulin anyway. Why? Because metformin doesn’t always control blood sugar tightly enough, especially in the third trimester when insulin resistance spikes. And while metformin crosses the placenta, there’s no clear evidence it causes birth defects. Still, some experts worry about its effect on the mTOR pathway, which plays a role in fetal growth.

The Endocrine Society says metformin can be used for gestational diabetes, but warns against adding it to insulin for women with preexisting type 2 diabetes. Why? Because it might increase the chance of having a small baby. Joslin Diabetes Center takes an even stricter stance, saying metformin shouldn’t be used beyond the first trimester unless absolutely necessary.

What Medications Are Off-Limits?

Not all diabetes pills are safe during pregnancy. In fact, most are off the table.

• GLP-1 receptor agonists (like semaglutide and liraglutide): These are banned. They’re linked to fetal growth issues in animal studies and have zero safety data in humans. The recommendation? Stop them before you even try to get pregnant.
• SGLT2 inhibitors (like dapagliflozin and empagliflozin): These increase the risk of dehydration and ketoacidosis in pregnancy. No reliable data. Avoid.
• DPP-4 inhibitors (like sitagliptin): Too little information. Not recommended.
• Alpha-glucosidase inhibitors (like acarbose): Rarely used even outside pregnancy, and completely untested in pregnant women.

Bottom line: if you’re on any of these medications and planning pregnancy, talk to your doctor now. Don’t wait until you’re pregnant to switch.

Glucose Targets: What “Good Control” Really Means

Normal blood sugar ranges don’t apply during pregnancy. The targets are tighter-and for good reason.

• Fasting: under 95 mg/dL (5.3 mmol/L)
• 1 hour after eating: under 140 mg/dL (7.8 mmol/L)
• 2 hours after eating: under 120 mg/dL (6.7 mmol/L)

These numbers come from the Endocrine Society and ACOG guidelines updated in 2023. Hitting them reduces your risk of complications by up to 50%. That’s why frequent monitoring matters. Many women check their blood sugar 4-7 times a day: before meals, after meals, and sometimes at bedtime.

Continuous glucose monitors (CGMs) are becoming more common, especially for women with type 1 diabetes. They show trends, not just snapshots, and can alert you to highs and lows before they become dangerous. For type 2 or gestational diabetes, the evidence isn’t as strong yet, but many providers still recommend them if you’re struggling with swings.

Preconception Planning: The Most Important Step

If you have diabetes and are thinking about getting pregnant, don’t wait until you’re pregnant to act. The best thing you can do for your baby is to get your HbA1c under control before conception.

The OHSU Diabetes and Pregnancy Program recommends an HbA1c below 6.5% before trying to conceive. If your HbA1c is above 10%, pregnancy is considered high-risk. Experts strongly advise using reliable birth control until your numbers improve. Why? Because the first 8 weeks of pregnancy are when the baby’s organs form-and that’s when high blood sugar causes the most damage.

Transitioning medications matters too. If you’re on metformin, your doctor may tell you to stop it once you’re pregnant or switch to insulin. If you’re on a GLP-1 agonist, you need to stop it at least 2-3 months before trying to conceive. And don’t forget: low-dose aspirin (81-100 mg daily) is often started at 12 weeks to prevent preeclampsia in women with preexisting diabetes.

What Happens After Delivery?

Many women assume their diabetes will disappear after birth. For gestational diabetes, that’s often true-but not always. About half of women who had gestational diabetes will develop type 2 diabetes within 10 years. So even if you stop insulin or metformin after delivery, you still need follow-up testing at 6-12 weeks postpartum and then every 1-3 years.

For women with type 1 or type 2 diabetes, insulin needs drop sharply after delivery. You might need only half your pre-pregnancy dose. That’s why checking your blood sugar more often in the first few days after birth is critical-hypoglycemia risk spikes.

And yes, if you’re breastfeeding, insulin is safe. So is metformin. Small amounts pass into breast milk, but no harmful effects have been reported in babies. Most providers encourage breastfeeding-it helps stabilize your blood sugar and lowers your long-term diabetes risk.

What’s Next? Research Gaps and Real-World Challenges

Despite all the guidelines, big questions remain. We still don’t know the long-term effects of metformin exposure in the womb. Are these kids more likely to be overweight or develop insulin resistance later? Studies are ongoing.

Also, access to care varies. Women in rural areas or without good insurance often can’t get CGMs, frequent ultrasounds, or endocrinology support. That’s why some still rely on outdated practices-even though we have better tools now.

And while global health groups like the WHO are pushing for standardized care, the reality is that not every clinic follows the 2023 Endocrine Society guidelines. If your provider isn’t familiar with insulin analogs or CGMs, ask for a referral to a maternal-fetal medicine specialist or a diabetes in pregnancy clinic.

The bottom line? You’re not alone. Thousands of women manage diabetes successfully during pregnancy every year. With the right plan, the right team, and the right medications, you can have a healthy pregnancy and a healthy baby.