Can I take human insulin while pregnant or breastfeeding?

8.1 Pregnancy Risk Summary Available data from published studies over decades have not established an association with human insulin use during pregnancy and major birth defects, miscarriage, or adverse maternal or fetal outcomes ( see Data). There are risks to the mother and fetus associated with poorly controlled diabetes in pregnancy ( see Clinical Considerations). Animal reproduction studies were not performed. The estimated background risk of major birth defects is 6-10% in women with pre-gestational diabetes with a HbA1c >7% and has been reported to be as high as 20-25% in women with a HbA1c >10%. The estimated background risk of miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Prescribing label, section “8.1 Pregnancy” (opening excerpt): Humulin R U-500 KwikPen (subcutaneous), Eli Lilly and Company. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.

This quote is from the subcutaneous formulation label.

Mothers with diabetes using insulin may nurse their infants. Exogenous insulin is excreted into breastmilk, including newer biosynthetic insulins (e.g., aspart, deglutec, detemir, glargine glulisine, lispro). Even direct administration of recombinant insulin orally to preterm infants is safe.[1] Insulin is a normal component of breastmilk and may decrease the risk of type 1 diabetes in breastfed infants.[2-5] Women taking insulin for type 2 diabetes have higher milk insulin levels than those controlled with diet alone.[6]

Insulin requirements are reduced postpartum in women with type 1 diabetes,[7,8] although postpartum insulin requirements do not significantly differ between breastfeeding and non-breastfeeding women.[9] In general, insulin requirements are 30% to 50% lower than prepregnancy dosages immediately postpartum. Then the insulin requirements during breastfeeding average 21% lower than prepregnancy dosages, but there is wide variation.[8,10] In one study, insulin requirements were lower than prepregnancy dosage only during the first week postpartum: 54% of prepregnancy dosage on day 2 and 73% on day 3 postpartum. On day 7 postpartum, insulin dosage returned to prepregnancy requirements.[11] Another study found that dosage requirements did not return to normal for up to 6 weeks in some mothers.[12] A third study found that at 4 months postpartum, patients with type 1 diabetes who exclusively breastfed had an average of 13% lower (range −52% to +40%) insulin requirement than their prepregnancy requirement.[13] A retrospective case-control study found a 34% decrease in postpartum insulin requirement compare to preconception values. There was a nonsignificant trend towards lower requirements in exclusively breastfeeding mothers compared to partial or full formula feeding.[6] A small study found that mothers on insulin pumps were found to have an average basal insulin rates 14% lower and carbohydrate-to-insulin ratios were 10% higher than pre-pregnancy settings.[14] Breastfeeding appears to improve glucose postpartum glucose tolerance in mothers with gestational diabetes mellitus and in normal women.[15-17]

A small, well-controlled study of women with type 1 diabetes mellitus using continuous subcutaneous insulin found that the average basal insulin requirement in women with type 1 diabetes who breastfed was 0.21 units/kg daily and the total insulin requirement was 0.56 units/kg daily. In similar women who did not breastfeed, the basal insulin requirement was 0.33 units/kg daily and the total insulin requirement was 0.75 units/kg daily. The 36% lower basal insulin requirement was thought to be caused by glucose use for milk production.[18]

Lactation onset occurs later in patients with type 1 diabetes than in women without diabetes, with a greater delay in mothers with poor glucose control.[11,19] Mothers with type 1 diabetes also discontinue nursing at a higher rate during the first week postpartum.[20-22] Women with any form of diabetes during pregnancy had more problems with low milk supply than women without diabetes.[23] Once established, lactation persists as long in mothers with diabetes as in mothers without diabetes.[19,24] However, as in women without diabetes, smoking has a strong negative impact on lactation among mothers with type 1 diabetes.[13,25] Other factors that have been identified as causes of shorter duration of breastfeeding among type 1 diabetic patients are more frequent caesarean sections and earlier delivery.[26] Among patients with gestational diabetes, those treated with insulin have a delayed onset of lactogenesis II and lower exclusive breastfeeding rates compared to those not treated with insulin.[27,28]

“Summary of Use during Lactation”, LactMed record “Insulin” (LM147), quoted verbatim. Everything LactMed reports about Insulin while breastfeeding.

8.2 Lactation Risk Summary Available data from published literature suggests that exogenous human insulin products, including HUMULIN R U-500, are transferred into human milk. There are no adverse reactions reported in breastfed infants in the literature. There are no data on the effects of exogenous human insulin products, including HUMULIN R U-500 on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for HUMULIN R U-500 and any potential adverse effects on the breastfed child from HUMULIN R U-500 or from the underlying maternal condition.

Prescribing label, section “8.2 Lactation”: Humulin R U-500 KwikPen (subcutaneous), Eli Lilly and Company. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.

This quote is from the subcutaneous formulation label.