Diabetes Medications During Pregnancy: Insulin vs. Oral Options Explained

Managing Diabetes in 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 short answer: insulin is still the gold standard. But it’s not the only option. Oral medications like metformin are used too, though with important limits. The goal isn’t just to keep your blood sugar in range-it’s to protect your baby from complications like excessive birth weight, early delivery, or low blood sugar after birth.

Here’s what actually works, what’s risky, and what you should avoid. No fluff. Just what the latest guidelines from the Endocrine Society, ACOG, and Joslin Diabetes Center say as of 2025.

Why Blood Sugar Control Matters So Much

High blood sugar during pregnancy doesn’t just affect you. It crosses the placenta. Your baby’s pancreas responds by making more insulin, turning extra glucose into fat. That’s why babies of mothers with uncontrolled diabetes are more likely to be large for gestational age (LGA), face breathing problems at birth, or end up in the NICU.

The targets are strict-and for good reason:

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

These aren’t suggestions. They’re based on data from thousands of pregnancies. Hitting them cuts the risk of complications by nearly half. That’s why treatment starts early-even before you’re pregnant, if possible.

Insulin: The Go-To Choice, No Surprises

Insulin is the most studied and safest medication for diabetes in pregnancy. It doesn’t cross the placenta, so it doesn’t reach your baby. That’s why doctors start here, whether you have type 1, type 2, or gestational diabetes that won’t respond to diet and exercise.

Not all insulins are the same. Here’s what’s recommended:

• Rapid-acting analogs (lispro, aspart): Best for meals. They work fast, clear quickly, and lower the risk of low blood sugar compared to older regular insulin.
• Long-acting analogs (detemir, glargine): Used for background control. Detemir has solid data in pregnancy. Glargine is considered safe based on multiple studies involving over 700 women.
• Avoid: Glulisine and degludec. There’s not enough safety data yet. Don’t risk it.

Many women switch from pills to insulin once pregnant. That’s normal. Your body changes fast-your insulin needs can double or triple by the third trimester. That’s not a sign you’re failing. It’s biology.

Metformin: The Controversial Oral Option

Metformin is the only oral medication with enough data to be used in pregnancy. It’s cheaper, easier to take than injections, and studies show it lowers the risk of having a very large baby, preeclampsia, and neonatal hypoglycemia compared to insulin.

But here’s the catch:

• It crosses the placenta. Your baby is exposed to it.
• About half of women on metformin still need insulin later in pregnancy because metformin alone isn’t enough.
• Some studies suggest possible long-term effects on the baby’s metabolism, though no clear harm has been proven yet.

The Endocrine Society says metformin can be used for gestational diabetes-but not as an add-on to insulin in type 2 diabetes. Why? Because adding it increases the risk of having a small baby, and the benefits don’t outweigh that risk.

Joslin Diabetes Center takes a harder line: they say metformin shouldn’t be used beyond the first trimester. Other centers use it longer. This is where you need to talk to your doctor. There’s no universal rule.

What You Should Avoid Completely

Some diabetes drugs are off-limits during pregnancy. Period.

• GLP-1 receptor agonists (like semaglutide, liraglutide): These are linked to birth defects in animal studies. The Endocrine Society recommends stopping them before conception-not when you find out you’re pregnant.
• SGLT2 inhibitors (like empagliflozin, dapagliflozin): These cause fetal malformations in animals and have zero human safety data in pregnancy. Don’t use them.
• DPP-4 inhibitors (like sitagliptin) and alpha-glucosidase inhibitors (like acarbose): Too little data. Avoid unless in a rare, monitored research setting.

If you’re on any of these and planning pregnancy, talk to your doctor now. Switching to insulin before conception is safer than trying to manage it once you’re pregnant.

Preconception Planning: The Most Important Step

Waiting until you’re pregnant to fix your diabetes is risky. The first 8 weeks of pregnancy are when your baby’s organs form-and that’s often before you even know you’re pregnant.

Here’s what you need to do ahead of time:

• Get your HbA1c below 6.5%. If it’s above 10%, delay pregnancy. Use birth control until your numbers are stable.
• Stop unsafe medications. Switch to insulin or metformin (if appropriate) before trying to conceive.
• Start taking 81-100 mg of aspirin daily from week 12. This reduces your risk of preeclampsia, which is much higher if you have diabetes.
• See an endocrinologist and high-risk OB together. Team care saves lives.

Women who plan ahead have dramatically better outcomes. It’s not about being perfect-it’s about being prepared.

During Labor and Delivery: What to Expect

Even if your diabetes is well-controlled, labor is a stress test. Your body’s hormones can spike your blood sugar fast.

Hospital teams will monitor your glucose every hour. You’ll likely get IV insulin if needed. You won’t be left to manage it alone. Insulin pumps can usually continue during labor, but your team will adjust settings.

After birth, your insulin needs drop fast-sometimes by 50% in the first 24 hours. Watch for low blood sugar. If you’re breastfeeding, you’ll need to eat more often and check your sugar more closely.

After Delivery: What Happens to Your Medications?

Good news: most women with gestational diabetes stop all medications after delivery. Your blood sugar usually returns to normal.

If you had type 2 diabetes before pregnancy, you’ll likely need to restart your pre-pregnancy meds-or switch back to insulin if you stopped it. Metformin is safe while breastfeeding. Insulin is safe too-it doesn’t pass into breast milk.

Don’t assume you’re "cured" after birth. Women with gestational diabetes have a 50% chance of developing type 2 diabetes within 10 years. Get tested 6-12 weeks after delivery, then every 1-3 years.

What’s Still Unknown

Science hasn’t answered everything. We don’t know yet if metformin exposure in the womb affects a child’s weight or risk of diabetes later in life. We don’t know if newer insulins like degludec are truly safe. We don’t have enough data on continuous glucose monitors (CGMs) for type 2 diabetes in pregnancy.

That’s why guidelines stay cautious. Insulin remains the default because we know it works. Everything else comes with questions.

Bottom Line: What to Do Now

If you’re pregnant and on diabetes meds:

• Stick to insulin unless your doctor says otherwise.
• Metformin? Maybe-but only if you’re on it before pregnancy and your doctor agrees.
• Stop GLP-1 agonists, SGLT2 inhibitors, and DPP-4 inhibitors now.
• Check your blood sugar daily. Use a meter or CGM if recommended.
• See your endocrinologist and OB together, every 2-4 weeks.

If you’re planning pregnancy:

• Get your HbA1c below 6.5%.
• Switch to safe meds before conceiving.
• Start low-dose aspirin at 12 weeks.
• Don’t wait until you’re pregnant to fix this.

Diabetes in pregnancy is manageable. It’s not easy-but with the right plan, most women have healthy babies. The key is acting early, staying informed, and trusting your care team.