Diabetes Medications During Pregnancy: Insulin vs. Oral Options Explained

Managing diabetes during pregnancy isn’t just about keeping blood sugar in range-it’s about protecting two lives at once. Whether you had diabetes before getting pregnant or developed gestational diabetes (GDM) during pregnancy, the choices you make around medication matter. Not all diabetes drugs are safe during pregnancy. Some can cross the placenta and affect your baby’s development. Others, like insulin, have decades of safety data behind them. Understanding what works, what doesn’t, and why can ease the stress and help you make confident decisions.

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 your baby. That’s why it’s the first-line treatment for both type 1, type 2, and gestational diabetes when diet and exercise aren’t enough. The Endocrine Society’s 2023 guidelines confirm insulin remains the safest option for all stages of pregnancy.

Not all insulins are created equal. Rapid-acting analogs like insulin lispro and insulin aspart are preferred over regular human insulin because they work faster after meals and cause fewer low blood sugar episodes. Long-acting options like insulin detemir and insulin glargine are also considered safe based on multiple studies involving hundreds of pregnant women. One 2019 NIH review of 702 women found no significant difference in outcomes between glargine and the older NPH insulin.

But not all newer insulins are cleared yet. Insulin glulisine and degludec don’t have enough data to recommend them during pregnancy. Doctors avoid them unless there’s no other choice. If you’re on an insulin pump (CSII), you can keep using it. Studies show it helps lower HbA1c and reduces insulin needs by delivery-but it doesn’t change the risk of big babies or NICU stays compared to multiple daily injections.

Metformin: A Common Oral Option, But With Caveats

Metformin is the most studied oral medication for gestational diabetes. It’s cheaper than insulin, taken as a pill, and doesn’t require injections. Some studies show it leads to fewer large-for-gestational-age babies, less neonatal hypoglycemia, and lower rates of preeclampsia compared to insulin. One 2019 NIH meta-analysis found metformin cut the odds of having a very large baby by 35%.

But here’s the catch: about half of women on metformin end up needing insulin anyway because their blood sugar stays too high. And while metformin crosses the placenta, there’s no clear evidence it causes birth defects. Still, experts are worried about how it might affect your baby’s long-term metabolism. Animal studies suggest it could interfere with the mTOR pathway, which plays a role in growth and development.

The Endocrine Society doesn’t recommend adding metformin to insulin for women with preexisting type 2 diabetes. Why? Because it increases the risk of having a small-for-gestational-age baby, and the benefits don’t outweigh that risk. Joslin Diabetes Center takes an even stricter stance: they say metformin shouldn’t be used beyond the first trimester or as a substitute for insulin.

If you’re on metformin before pregnancy, your doctor will likely tell you to stop it before conception or during the first trimester and switch to insulin. It’s not because it’s dangerous-it’s because we don’t know enough about long-term effects, and insulin is safer.

What Oral Medications Are Off-Limits?

Not all diabetes pills are safe in pregnancy. In fact, most aren’t.

• GLP-1 receptor agonists (like semaglutide, liraglutide) are strictly off-limits. These drugs are linked to fetal loss in animal studies and have almost no human pregnancy data. The Endocrine Society recommends stopping them before conception-not after you find out you’re pregnant.
• SGLT2 inhibitors (like empagliflozin, dapagliflozin) are also not recommended. They increase the risk of dehydration and ketoacidosis during pregnancy, and fetal safety data is lacking.
• DPP-4 inhibitors (like sitagliptin) and alpha-glucosidase inhibitors (like acarbose) have no reliable safety data in pregnancy. Don’t use them.

There’s a real gap here. For women who can’t tolerate insulin or don’t want injections, the options are extremely limited. That’s why so many end up switching to insulin-even if they were managing fine on pills before pregnancy.

What About Blood Sugar Targets?

Normal blood sugar goals for non-pregnant adults don’t apply here. During pregnancy, you need tighter control to protect your baby.

The Endocrine Society and ACOG agree on these targets:

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

These numbers aren’t arbitrary. Studies show that keeping blood sugar below these levels reduces the risk of having a baby over 9 pounds, needing NICU care, or developing preeclampsia. Monitoring is key. Most 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 help catch highs and lows you might miss with finger sticks. But for type 2 diabetes or gestational diabetes, the evidence doesn’t yet prove CGMs are better than traditional finger-prick testing. Still, if your doctor recommends one, it can be a helpful tool.

Preconception Planning Matters More Than You Think

If you’re planning to get pregnant and have diabetes, the best time to optimize your health is before you conceive. Your baby’s organs form in the first 8 weeks-often before you even know you’re pregnant.

The OHSU Diabetes and Pregnancy Program recommends an HbA1c below 6.5% before conception. If your HbA1c is above 10%, they strongly advise against pregnancy until your levels are better controlled-and offer long-acting birth control to help you plan.

That means:

• Switching from unsafe meds (like GLP-1RAs) to insulin before trying to conceive
• Getting your blood sugar under control for at least 3-6 months
• Talking to your endocrinologist and OB-GYN together

Many women don’t realize this step is critical. They assume they can just start taking insulin once they’re pregnant. But the earlier you stabilize your numbers, the lower the risk of miscarriage and birth defects.

What Happens During Labor and After Delivery?

During labor, your blood sugar can swing wildly. That’s why hospitals monitor it hourly. You might need IV insulin to keep it steady. Your baby’s blood sugar will also be checked right after birth-babies of mothers with diabetes are at higher risk for low blood sugar.

After delivery, things change fast. If you had gestational diabetes, you’ll likely stop all medications. Insulin and metformin are usually discontinued unless you have type 2 diabetes. Your blood sugar will be checked again 6-12 weeks postpartum to see if you still have diabetes.

If you had type 1 or type 2 diabetes before pregnancy, you’ll continue your treatment-but your insulin needs will drop sharply after birth. Many women need only half their pregnancy dose within days of delivery. Your doctor will adjust your doses carefully to avoid low blood sugar.

What About Breastfeeding?

Good news: most diabetes medications are safe while breastfeeding.

Insulin is perfectly safe-it doesn’t pass into breast milk. Metformin passes in tiny amounts, but studies show no harm to babies. The American Academy of Pediatrics considers it compatible with breastfeeding.

GLP-1RAs and SGLT2 inhibitors? Avoid them. There’s not enough data to say they’re safe for nursing babies. Stick with insulin or metformin if you’re breastfeeding.

Final Thoughts: Safety First, Flexibility Second

There’s no perfect solution. Insulin requires injections and careful dosing. Metformin is easier to take but often isn’t enough. Other pills are off the table. The goal isn’t to find the easiest option-it’s to find the safest one for you and your baby.

Work with a team: an endocrinologist, a maternal-fetal medicine specialist, a diabetes educator, and a dietitian. Don’t try to manage this alone. Your body is changing every day, and your treatment plan should change with it.

Remember: you’re not failing if you need insulin. You’re doing exactly what’s needed to give your baby the best start.