GLP-1 and GLP-1/GIP Agonists During Breastfeeding
No GLP-1 receptor agonist or GLP-1/GIP dual agonist is currently recommended for use during breastfeeding due to insufficient human safety data, and all should be discontinued during lactation. 1, 2
Current Guideline Recommendations
The most recent and authoritative guidance comes from multiple sources that uniformly advise against use:
The 2023 JAMA obesity management review explicitly states that all GLP-1 receptor agonists should not be used during pregnancy or lactation, with the sole exception being metformin (which is not a GLP-1 agonist). 1
The 2025 EULAR recommendations for antirheumatic drugs note that GLP-1 receptor agonists have unknown safety during lactation and should be avoided. 1
The 2018 CHEST atrial fibrillation guidelines state that no clinical data on the effect of NOACs (which includes discussion of novel agents) on breast-fed infants are available, and the recommendation is against use of these medications in breast-feeding women. 1
Available Human Evidence on Milk Transfer
Semaglutide (Most Studied)
The only direct human data available comes from a 2024 study examining semaglutide transfer into breast milk:
Semaglutide was not detected in any human milk samples collected at 0,12, and 24 hours post-administration from eight lactating women. 3
Even using a worst-case scenario calculation with the lower limit of quantification (5.7 ng/mL), the projected relative infant dose (RID) was only 1.26%—well below the 10% safety threshold typically considered acceptable. 3
However, this study acknowledges that questions about long-term infant outcomes, maternal nutrient intake adequacy, and breast milk nutrient content remain unanswered. 3
Other GLP-1 Agonists
Animal studies show that GLP-1 agonists are excreted in breast milk, but human data on excretion are not available for agents other than semaglutide. 2
Exenatide showed minimal maternal-to-fetal transfer in placental studies, but this does not inform breast milk transfer. 2
GLP-1/GIP Dual Agonist (Tirzepatide)
No human data exist regarding tirzepatide transfer into breast milk or effects on breastfed infants. 4, 5
Given its structural similarity to GLP-1 agonists and mechanism involving delayed gastric emptying, the same precautions should apply. 1, 4
Critical Safety Concerns Beyond Milk Transfer
Maternal Nutritional Status
GLP-1 agonists cause significant appetite suppression and reduced caloric intake, which could compromise maternal nutrition during lactation when caloric demands are increased by 450-500 calories/day. 6, 7
Inadequate maternal nutrition directly affects breast milk composition and volume, potentially harming infant growth and development. 3
Gastrointestinal Effects
- Nausea occurs in 17-44% of patients, vomiting in 7-25%, and diarrhea in 12-32%, which could lead to maternal dehydration and electrolyte imbalances that affect milk production. 8, 4
Pharmacokinetic Considerations
The prolonged half-lives of long-acting GLP-1 agonists (semaglutide: ~7 days; dulaglutide: ~5 days; tirzepatide: ~5 days) mean that even minimal milk transfer could result in cumulative infant exposure over time. 5
Structural modifications including fatty acid conjugation and albumin binding that prolong half-life also increase the theoretical risk of milk transfer. 5
Clinical Decision Algorithm
If a breastfeeding woman requires weight management or diabetes control:
Discontinue all GLP-1 agonists and GLP-1/GIP dual agonists immediately upon deciding to breastfeed. 1, 2
For diabetes management during lactation, use metformin as first-line (safe and recommended by ACOG as second-line for diabetes in pregnancy; safe during lactation). 1
For weight management during lactation, prioritize lifestyle modifications (diet and exercise) rather than pharmacotherapy. 1, 6
If the patient has cardiovascular disease requiring GLP-1 agonist therapy, counsel regarding formula feeding as an alternative to allow medication continuation. 6, 8
Wait at least 5-7 half-lives after the last dose before initiating breastfeeding if the medication was used peripartum (approximately 5-7 weeks for semaglutide, dulaglutide, or tirzepatide). 5
Common Pitfalls to Avoid
Do not assume that the single semaglutide study showing undetectable milk levels provides sufficient evidence for safety—long-term infant neurodevelopmental outcomes have not been studied. 3
Do not extrapolate safety data from pregnancy studies to lactation—placental transfer and milk transfer involve different mechanisms. 2
Do not rely on the low RID calculation alone—the 10% threshold was developed for drugs with established safety profiles, not novel peptide therapeutics with unknown long-term effects. 3
Do not overlook the indirect risks of maternal malnutrition and dehydration from medication side effects on milk production and composition. 3, 4