Managing diabetes during pregnancy isn’t just about keeping blood sugar in range-it’s about protecting two lives at once. Whether you have type 1, type 2, or gestational diabetes, the medications you take can make a real difference in how your baby grows and whether you avoid serious complications like preeclampsia, preterm birth, or a baby that’s too large to deliver safely. But not all diabetes drugs are safe during pregnancy. Some are proven and trusted. Others are off-limits. And a few sit in a gray zone where doctors debate the risks.
Why Insulin Is Still the Gold Standard
Insulin is the most widely used and safest medication for diabetes during pregnancy. It doesn’t cross the placenta, so it doesn’t reach the baby. That’s why doctors turn to insulin first-whether you had diabetes before getting pregnant or developed it during pregnancy.
There are two main types of insulin used: rapid-acting and long-acting. Rapid-acting insulins like insulin lispro and insulin aspart are preferred because they work quickly after meals and clear out fast, reducing the chance of low blood sugar later. Regular insulin is older and less predictable, so it’s rarely used anymore.
For background control, long-acting insulins like insulin detemir and insulin NPH are common. Studies show detemir works just as well as NPH without increasing risks to the baby. Insulin glargine is also used, with data from over 700 pregnancies showing it’s as safe as NPH. But newer insulins like glulisine and degludec? Not recommended yet. There’s just not enough data to say they’re safe.
Some women use insulin pumps (continuous subcutaneous insulin infusion, or CSII). These can help keep blood sugar steadier than multiple daily injections, especially in type 1 diabetes. But studies show the baby outcomes are about the same either way. The real benefit? Less stress for mom. Fewer spikes, fewer crashes.
Oral Medications: Metformin and the Controversy
Metformin is the only oral drug that’s even close to being a real alternative to insulin in pregnancy. It’s commonly used for type 2 diabetes and PCOS, and many women are already on it before they get pregnant. So, can they keep taking it?
The answer is… it’s complicated.
Large studies, including a 2019 NIH meta-analysis, found that women taking metformin for gestational diabetes had lower rates of large babies, fewer NICU admissions, less neonatal hypoglycemia, and lower risk of preeclampsia compared to those on insulin. That sounds great-until you dig deeper.
About half of women on metformin end up needing insulin anyway because their blood sugar stays too high. And here’s the big concern: metformin crosses the placenta easily. That means the baby is exposed to it throughout pregnancy. Some animal and early human studies suggest it might affect the mTOR pathway, which controls cell growth. That’s why some experts worry it could influence the baby’s long-term metabolism.
The Endocrine Society says: don’t add metformin to insulin if you have type 2 diabetes. They say the risk of having a small baby outweighs the benefit of fewer large babies. Joslin Diabetes Center goes even further-they say metformin shouldn’t be used beyond the first trimester, and never as a replacement for insulin.
So if you’re on metformin before pregnancy, your doctor might let you keep it through the first trimester while slowly switching you to insulin. But if you’re newly diagnosed with gestational diabetes, most providers will start with insulin unless you strongly prefer metformin and understand the unknowns.
What Medications Are Completely Off-Limits?
Not all diabetes pills are safe-or even allowed-during pregnancy. Here’s what you need to avoid:
- GLP-1 receptor agonists (like semaglutide, liraglutide): These are used for weight loss and type 2 diabetes, but they’re strictly off-limits during pregnancy. The Endocrine Society says stop them before you even try to conceive. There’s no safe window.
- SGLT2 inhibitors (like empagliflozin, dapagliflozin): These help the kidneys flush out sugar, but they’ve been linked to birth defects in animal studies. No human data exists because it’s unethical to test them in pregnant women. Don’t use them.
- DPP-4 inhibitors (like sitagliptin, linagliptin): Too little data. Avoid.
- Alpha-glucosidase inhibitors (like acarbose): Rarely used even outside pregnancy, and no safety data in pregnancy. Skip it.
These aren’t just "use with caution" drugs-they’re outright contraindicated. If you’re on any of these and planning pregnancy, talk to your doctor now. Switching takes time, and your blood sugar needs to be stable before conception.
What Are the Blood Sugar Targets?
It’s not enough to just take the right meds-you need to hit the right numbers. The goal isn’t "normal" blood sugar. It’s pregnancy-specific targets that reduce risks to the baby.
According to the Endocrine Society and ACOG (2023), aim for:
- 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 aren’t suggestions. They’re the benchmarks used in every major study linking good control to fewer complications. If your numbers are consistently above these, your doctor will adjust your meds-usually by increasing insulin.
Some women use continuous glucose monitors (CGMs). These devices track sugar levels 24/7 and can show trends you’d miss with finger sticks. For type 1 diabetes, CGMs are strongly recommended-they help avoid dangerous highs and lows. For type 2 or gestational diabetes, the evidence isn’t as strong, but many providers still recommend them if you’re on insulin.
Preconception Planning Matters More Than You Think
If you have type 1 or type 2 diabetes and are thinking about getting pregnant, the most important thing you can do is plan ahead. Waiting until you’re pregnant to get your blood sugar under control is risky.
High blood sugar in the first 8 weeks of pregnancy-when the baby’s organs are forming-is linked to birth defects. That’s why experts say your HbA1c should be under 6.5% before conception. If it’s above 10%, you’re at high risk. Some clinics will even recommend long-acting birth control until your numbers improve.
Here’s what to do before you get pregnant:
- Get your HbA1c tested. If it’s above 7%, work with your endocrinologist to bring it down.
- Stop GLP-1 agonists and SGLT2 inhibitors now-not when you find out you’re pregnant.
- Start taking a prenatal vitamin with at least 400 mcg of folic acid. It reduces neural tube defect risk.
- Get your eyes and kidneys checked. Diabetes can affect both, and pregnancy makes it worse.
- Discuss insulin switches with your doctor. If you’re on metformin, plan how and when to transition.
It’s not about being perfect. It’s about being prepared. Even lowering your HbA1c from 8% to 7% before pregnancy cuts your risk of complications by almost half.
What Happens During Labor and After Delivery?
During labor, your blood sugar can swing wildly. Stress, pain, and not eating can cause highs. Insulin needs can drop suddenly. That’s why hospitals monitor glucose hourly during labor. You might need an IV insulin drip to keep things steady.
After delivery, your body changes fast. Insulin needs drop dramatically-sometimes by 50% or more. That’s why women on insulin are at high risk of low blood sugar in the first 24-48 hours after birth. Nurses will check your sugar often and adjust doses quickly.
For gestational diabetes: most women stop all meds right after delivery. Your blood sugar usually returns to normal. But you’re at higher risk for type 2 diabetes later, so get tested 6-12 weeks after birth and then every 1-3 years.
For type 1 or type 2: you’ll likely resume your pre-pregnancy regimen, but your doses will need fine-tuning. Breastfeeding can lower blood sugar even more, so keep snacks handy.
What About Breastfeeding?
Good news: most diabetes medications are safe while breastfeeding.
Insulin? Perfectly safe. It doesn’t enter breast milk in meaningful amounts.
Metformin? Also safe. Only tiny amounts pass into milk, and studies show no harm to babies. Many moms continue it after delivery, especially if they have type 2 diabetes or PCOS.
But GLP-1 agonists? Still off-limits. No data. Wait until you’re done breastfeeding.
And don’t forget: breastfeeding helps your body recover from pregnancy diabetes. It lowers your risk of developing type 2 diabetes later. Even if you don’t breastfeed exclusively, every hour counts.
Bottom Line: What Should You Do?
If you have diabetes and are pregnant-or planning to be-here’s what you need to remember:
- Insulin is the safest, most reliable option. Don’t fear it. It’s been used for decades with excellent outcomes.
- Metformin can be used in early pregnancy if you’re already on it, but it’s not a replacement for insulin if your sugar stays high.
- Avoid all other oral diabetes pills. GLP-1s, SGLT2s, DPP-4s-they’re not worth the risk.
- Plan ahead. Get your HbA1c under 6.5% before conception. Stop unsafe meds now.
- Monitor closely. Hit those pregnancy targets. Use CGM if you can.
- Keep going after birth. Breastfeeding helps. Get tested for type 2 diabetes later.
There’s no perfect solution. Every choice comes with trade-offs. But with the right plan, the right team, and the right timing, you can have a healthy pregnancy-even with diabetes.