A breakthrough for postpartum moms: What new research really says about tirzepatide and breastfeeding
canva / motherly
“It’s not about racing to thinness. It’s about giving women safe, evidence-based options.”
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When Dr. Alexandra Sowa, a New York–based physician, opened Instagram to share a research update, she didn’t expect her post to resonate with thousands of new mothers. In a now-viral reel, she explains that low-dose tirzepatide (2.5–5 mg)—a GLP-1 medication more commonly known by brand names like Mounjaro—has been deemed safe for breastfeeding in preliminary data.
For a community of postpartum women who’ve felt excluded from weight-management and metabolic health conversations, the news felt like a turning point. “It’s not about racing to thinness,” Sowa wrote. “It’s about giving women safe, evidence-based options.”
What the science actually shows
According to LactMed, early evidence indicates that tirzepatide is barely detectable in breastmilk at doses up to 5 mg. In five mothers who provided milk samples throughout the week of their dose, no samples exceeded 2.38 mcg/L—the lab’s limit of quantification—and several were below detection entirely.
Even more reassuring: because tirzepatide is a large peptide molecule and is destroyed by enzymes in the stomach, it’s unlikely to be absorbed by the infant. In the small group studied, no adverse effects were reported in breastfed babies.
Still, LactMed urges caution, especially with newborns and preterm infants. The data are preliminary, and more research is needed to understand possible effects on milk supply—a point Dr. Sowa herself emphasized in the comments.
Related: Breastfeeding for weight loss is a harmful message for postpartum moms
Moms had questions — and Dr. Sowa answered
Under Dr. Sowa’s post, hundreds of women chimed in with questions. A few of the most common themes:
- “What!? No one said safe?” asked @Summerthedietitian
“All breastfeeding discussions need to be deeply informed and supported,” Sowa replied. “But for the right person, it can be safe. Breastfeeding plus any medicine/treatment has too long scared doctors and patients. This is great news.” - “Great to know! But how will it affect milk supply? Will it decrease it? Any info on that?” asked @Katya_glass.
“We need to study this — and it’s why I would advise not starting until solids have been introduced,” Sowa answered. “However, we do know that managing insulin resistance can actually increase supply.” - “Also the molecule is not meant to be digested, it would be destroyed by the enzymes in the stomach. That’s why it’s injected,” wrote @marilyngalindo.md
“Yes, that too!” Sowa responded. “It’s exciting to have the molecular knowledge confirmed in breast milk.”
This back-and-forth shows how eager mothers are for nuanced, evidence-based information about their own health.
Related: 70% of women have breastfeeding challenges. Can we stop pretending it’s easy?
Why this matters for mothers
For decades, breastfeeding parents have had to navigate a frustrating lack of data on how medications might affect their babies. Even widely used drugs are often labeled “not recommended” simply because no one studied them in lactating women—not because they’re known to be harmful.
This is why Sowa publicly thanked the Laura W. Bush Institute for Women’s Health for funding the research. Women’s health studies—especially around lactation—remain chronically underfunded. The result is a vacuum of information at exactly the time when new mothers are making critical health decisions.
What parents should know right now
- Talk to your provider. Every situation is different. The LactMed entry stresses that “all breastfeeding discussions need to be deeply informed and supported.”
- Consider timing. Because there’s no published data on supply yet, experts recommend caution during the exclusive-breastfeeding period and suggest waiting until solids are introduced if possible.
- Don’t self-stop breastfeeding. Preliminary data show no reason to discontinue nursing if a mother requires tirzepatide, but shared decision-making with a healthcare provider is key.
Breastfeeding moms deserve data
Sowa’s reel hit a nerve because it signaled something larger: breastfeeding parents deserve real data, not guesswork. As more postpartum women seek support for metabolic health, they need evidence-based guidance—not blanket warnings.
For now, the early findings are encouraging: low-dose tirzepatide appears barely detectable in milk and unlikely to be absorbed by infants. But the story isn’t finished. More studies are needed, and mothers deserve a seat at the research table.
Until then, this new information offers something rare in postpartum medicine: hope and choice—without forcing mothers to choose between their own health and their baby’s.
Sources:
LactMed. 2025. “Tirzepatide – Drugs and Lactation Database (LactMed®)”
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