Is Lantus (insulin glargine) safe during pregnancy?

Is Lantus Safe During Pregnancy?

Yes, Lantus (insulin glargine) is safe to use during pregnancy and is the preferred agent for managing diabetes in pregnancy, particularly for women already achieving good glycemic control with it prior to conception.

Primary Recommendation

Insulin is the preferred agent for management of both type 1 and type 2 diabetes in pregnancy 1. While the most recent 2025 American Diabetes Association guidelines do not specifically distinguish between insulin types, insulin glargine has accumulated substantial safety evidence over the past two decades.

Safety Evidence

FDA Classification and Human Data

• Published studies with insulin glargine during pregnancy have not reported a clear association with adverse developmental outcomes 2
• Trans-placental transfer studies demonstrate that insulin glargine does not cross the placenta when used at therapeutic concentrations 3
• The FDA drug label states there are no clear associations between insulin glargine and major birth defects, miscarriage, or adverse maternal or fetal outcomes when used during pregnancy 2

Clinical Outcomes Data

Observational studies consistently show favorable outcomes:

• Women using glargine during pregnancy (from preconception through delivery) demonstrated decreased maternal and neonatal adverse outcomes compared to NPH insulin 4
• Specifically, glargine-treated women had lower rates of retinopathy/nephropathy worsening, preeclampsia, microalbuminuria, and all types of hypoglycemia compared to NPH-treated women 4
• Neonatal outcomes were superior with glargine, including better Apgar scores, reduced ICU admissions, and fewer congenital malformations 4

Clinical Decision Algorithm

For Women Already on Glargine Pre-Pregnancy:

Continue insulin glargine if good glycemic control is achieved 3. The benefit of maintaining established control outweighs theoretical concerns, as poorly controlled diabetes poses definite risks including diabetic ketoacidosis, preeclampsia, spontaneous abortions, preterm delivery, major birth defects, stillbirth, and macrosomia 2.

For Women Starting Insulin in Pregnancy:

Either insulin glargine or NPH insulin are acceptable options 1. The choice should consider:

• Hypoglycemia risk (glargine has lower nocturnal hypoglycemia rates) 4
• Patient's ability to manage complex regimens
• Cost considerations

Delivery Method:

Multiple daily injections or continuous subcutaneous insulin infusion (pump) are both acceptable 1. Neither has proven superior during pregnancy 5.

Critical Maternal-Fetal Risk Context

The risks of poorly controlled diabetes far exceed any theoretical medication concerns:

• Poorly controlled diabetes increases maternal risk for diabetic ketoacidosis, preeclampsia, spontaneous abortions, preterm delivery, and delivery complications 2
• Fetal risks include major birth defects (6-10% with HbA1c >7%, up to 20-25% with HbA1c >10%), stillbirth, and macrosomia-related morbidity 2
• The background risk of major birth defects in the general population is only 2-4% 2

Important Caveats

Hypoglycemia Prevention

• First trimester carries highest hypoglycemia risk due to increased insulin sensitivity 1
• Insulin requirements drop dramatically (approximately 34% lower than pre-pregnancy) immediately postpartum with placental delivery 1
• Frequent glucose monitoring and insulin dose adjustments are essential throughout pregnancy 1

Monitoring Requirements

• Daily self-monitoring of blood glucose is mandatory, as HbA1c alone does not capture the complexity of glycemic control 5
• Insulin requirements increase progressively after midterm 5
• Target glucose levels during labor should be 4-8 mmol/L (72-144 mg/dL) to prevent neonatal hypoglycemia 5

Common Pitfall

Do not mix insulin glargine with short-acting insulins in the same syringe, as glargine may coprecipitate other insulins 6. This requires separate injections but does not diminish safety or efficacy.

Limitations of Current Evidence

While no randomized controlled trials specifically evaluate insulin glargine in pregnancy 3, the extensive observational data from case reports and cohort studies consistently demonstrate safety 3, 4. The absence of RCT data is offset by decades of real-world clinical experience showing no adverse signals and the FDA's acknowledgment of safety based on available human data 2.