Diabetes Medications During Pregnancy: Insulin vs. Oral Options Explained

Managing diabetes during pregnancy isn’t just about controlling blood sugar-it’s about protecting two lives. Whether you have type 1, type 2, or gestational diabetes, the medications you take can make a real difference in your baby’s health. But not all diabetes drugs are safe during pregnancy. Some are gold standard. Others are off-limits. And a few sit in a gray zone where doctors debate the risks. So what’s actually safe? And what should you avoid?

Insulin: The Gold Standard for Pregnancy

Insulin is the most trusted medication for diabetes during pregnancy. It doesn’t cross the placenta, so it doesn’t reach your baby. That’s why it’s been the go-to choice for decades. The Endocrine Society’s 2023 guidelines reaffirm insulin as the first-line treatment for both preexisting diabetes and gestational diabetes that can’t be controlled with diet and exercise alone.

Not all insulins are the same. Rapid-acting analogs like insulin lispro and insulin aspart are preferred over regular human insulin because they work faster and clear quicker after meals. This means tighter control of post-meal spikes-something critical for reducing risks like large babies and neonatal hypoglycemia. Long-acting insulins like detemir and glargine have been studied in hundreds of pregnant women. Evidence shows they’re as safe as older NPH insulin, with no increased risk of birth defects or complications.

But here’s the catch: insulin glulisine and degludec? Not recommended. There’s simply not enough data to say they’re safe. If you’re on one of these before pregnancy, your doctor will switch you before you conceive. The same goes for insulin pumps. They’re safe to use during pregnancy, and many women find them easier to manage than multiple daily injections. Studies show slightly lower HbA1c levels and less insulin needed at delivery, but overall baby outcomes are similar.

Metformin: The Controversial Oral Option

Metformin is the only oral medication with enough data to be considered for use in pregnancy. It’s commonly prescribed for gestational diabetes, especially in places where insulin access is limited. A 2019 NIH meta-analysis found that women taking metformin had lower rates of large-for-gestational-age babies, preeclampsia, and NICU admissions compared to those on insulin.

But there’s a big downside. About half of women on metformin end up needing insulin anyway because their blood sugar stays too high. And while metformin doesn’t cause birth defects, it crosses the placenta easily. That means your baby is exposed to it throughout pregnancy. Some animal studies suggest it might affect the mTOR pathway-a key regulator of fetal growth-which raises questions about long-term metabolic effects on the child.

The Endocrine Society says metformin can be used in gestational diabetes, but not as an add-on to insulin for women with type 2 diabetes. Their reasoning? The potential benefit of fewer large babies doesn’t outweigh the risk of having a small-for-gestational-age baby. Joslin Diabetes Center takes an even stricter stance: they say metformin shouldn’t be used beyond the first trimester, and never as a replacement for insulin.

If you’re on metformin before pregnancy, most guidelines recommend stopping it before conception or switching to insulin during the first trimester. It’s not because it’s dangerous-it’s because we don’t know enough about the long-term effects on the baby’s future health.

What’s Completely Off-Limits

Several popular diabetes drugs have no place in pregnancy. GLP-1 receptor agonists like semaglutide (Ozempic) and liraglutide (Victoza) are off the table. These drugs are linked to fetal loss and developmental issues in animal studies. The Endocrine Society says you should stop them before trying to get pregnant-not during early pregnancy. Waiting until you find out you’re pregnant is too late.

SGLT2 inhibitors (like dapagliflozin and empagliflozin) are also not safe. They increase the risk of ketoacidosis during pregnancy and have no proven safety data. DPP-4 inhibitors (like sitagliptin) and alpha-glucosidase inhibitors (like acarbose) are similarly not recommended. There’s just not enough evidence to support their use.

This leaves a big gap. For women who can’t tolerate insulin or want to avoid injections, there are almost no safe oral alternatives. That’s why so many women end up on insulin-even if they’ve never needed it before pregnancy.

What You Need Before You Get Pregnant

Good diabetes control before conception is the single biggest factor in preventing birth defects and complications. The OHSU Diabetes and Pregnancy Program recommends an HbA1c below 6.5% before you get pregnant. If your HbA1c is above 10%, pregnancy is considered high-risk, and you’ll be strongly advised to delay conception until your levels are better controlled.

That means working with your endocrinologist and OB-GYN months in advance. You might need to switch medications, adjust your diet, or start using a continuous glucose monitor (CGM). Even if you’ve had diabetes for years, pregnancy changes how your body handles insulin. Your insulin needs can double or triple by the third trimester.

Aspirin is another preconception must. Women with preexisting diabetes are at higher risk for preeclampsia. ACOG, Joslin, and OHSU all recommend starting low-dose aspirin (81-100 mg daily) at 12 weeks to reduce that risk. It’s simple, cheap, and backed by solid evidence.

What Happens During Labor and After Delivery

During labor, your blood sugar will be checked every hour. High blood sugar during delivery can cause your baby’s blood sugar to crash right after birth. To prevent this, many hospitals use IV insulin drips to keep your levels steady. If you’re on an insulin pump, you’ll likely switch to IV insulin during labor.

After delivery, things change fast. Your insulin needs drop dramatically-often by 30-50%-because the placenta, which caused insulin resistance, is gone. If you had gestational diabetes, you’ll likely stop all medications right after birth. Your doctor will check your blood sugar before you leave the hospital and schedule a follow-up glucose test at 6-12 weeks to see if your diabetes resolved.

If you had type 1 or type 2 diabetes before pregnancy, you’ll resume your pre-pregnancy regimen, but your doses will need careful adjustment. Breastfeeding is safe with insulin and metformin. Both are considered compatible with nursing. Insulin doesn’t pass into breast milk. Metformin passes in tiny amounts, and no adverse effects have been reported in breastfed babies.

Why Insulin Still Wins

Even with newer drugs and better data, insulin remains the safest, most predictable option. It’s been used for over 90 years in pregnancy. We know its effects. We know how to adjust it. We know how to respond when things go wrong.

Metformin is tempting because it’s a pill. But the trade-offs are real. You might need insulin anyway. You might be exposing your baby to something we don’t fully understand. And if your blood sugar isn’t tight, the risks to your baby-preterm birth, shoulder dystocia, breathing problems-go up.

The bottom line? If you’re planning pregnancy and have diabetes, start with insulin. Work with your care team early. Get your HbA1c under control. Use glucose monitoring. Don’t wait until you’re pregnant to make changes. The best outcomes come from preparation-not last-minute fixes.

What About Future Options?

Researchers are looking into newer insulin analogs and safer oral drugs. But progress is slow. Ethical barriers make it hard to run large trials in pregnant women. The WHO is working on global guidelines to standardize care, but they won’t be ready until late 2025.

For now, the science is clear: insulin works. It’s safe. It’s effective. And until something better comes along, it’s still the best choice for keeping both mother and baby healthy.