GLP-1 drugs and breastfeeding: what the evidence actually says

What did @missqueenkayy92 actually say?

The creator claims the FDA has released new labeling data showing tirzepatide is effectively safe for breastfeeding mothers, citing a study where breast milk concentrations were "undetectable in 164 out of 171 samples" after a single 5mg dose. She also says she personally used tirzepatide while breastfeeding after her daughter turned 12 months, consulted her pediatrician, and concludes that "it does not transfer or hardly if any transfers into breast milk." She frames this as definitive proof that breastfeeding mothers can safely use tirzepatide.

She also adds a mechanistic explanation: that tirzepatide is "absorbed through your fat" after subcutaneous injection, and that whatever trace amounts reach breast milk get "wiped away in the gut" of the infant because the drug isn't processed orally. That last claim deserves real scrutiny.

Does the science back this up?

The FDA label data she cites is real, but "real data" and "proof of safety" are not the same thing. The study had 11 participants, used a single 5mg dose, and measured transfer over 28 days. It tells us about pharmacokinetic transfer. It does not tell us about infant outcomes.

The labeling change referenced in the video does appear in the updated prescribing information for Zepbound and Mounjaro, which now includes lactation pharmacokinetic data. The relative infant dose (RID) calculated from those measurements is well below the 10% threshold pharmacologists typically use as a rough safety benchmark (Hale, 2023, Medications and Mothers' Milk). That is genuinely reassuring data.

However, the study measured a single dose in healthy adult women, not the steady-state concentrations that would build up with weekly injections. Repeat dosing kinetics in lactating women have not been published. The FDA label itself still states that the developmental effects on breastfed infants are unknown. That caveat is doing a lot of work, and the creator does not mention it once.

What did they get wrong (or right)?

Credit where it is due: the pharmacokinetic data she quotes is accurate. The 164 out of 171 undetectable samples and the less than 0.02% maternal dose figure match the published labeling language. She correctly identifies tirzepatide as the active ingredient in both Mounjaro and Zepbound. She did consult a pediatrician, which is more than most people promoting this topic online bother to do.

Where she goes wrong is the leap from "low transfer" to "it is okay and it is safe and it is fine." That is not what the data says. Low transfer is necessary but not sufficient for a safety conclusion. GLP-1 receptors are expressed in neonatal gut tissue, and there is no published clinical data on what even trace tirzepatide exposure does to an infant's developing gut, pancreas, or appetite regulation (Drucker, 2022, Cell Metabolism).

Her claim that tirzepatide gets "wiped away in the gut" by the baby is a reasonable hypothesis, but it is not established pharmacology. Large peptides like tirzepatide are generally degraded in the GI tract, which does support low oral bioavailability. But "generally degraded" in adults does not automatically translate to neonates, whose gut permeability and enzyme maturity differ significantly from adults (Neu, 2007, Journal of Pediatrics).

What should you actually know?

The new FDA labeling data is a meaningful step forward, not a green light. Here is what it actually gives us: a small single-dose study suggesting very low breast milk transfer. Here is what it does not give us: steady-state transfer data with weekly dosing, infant plasma concentration measurements, or any clinical outcome data in breastfed infants.

The FDA label change reflects the pharmacokinetic data, not a safety determination for infants. The label language is specific: "available data on tirzepatide use in lactating women are insufficient to evaluate drug-related risks to the breastfed infant." That sentence still exists in the prescribing information right alongside the transfer data the creator quotes.

• The LactMed database (NIH) currently lists tirzepatide as having insufficient data to make a breastfeeding recommendation.
• Semaglutide, a related GLP-1 agonist, also shows low breast milk transfer in limited data, but carries the same insufficient-evidence caveat (Drugs and Lactation Database, 2024).
• Any breastfeeding mother considering tirzepatide should have this conversation with both her prescribing physician and her infant's pediatrician, not just one of them.
• Older infant age (12 months and beyond) is a reasonable personal risk-reduction strategy, as the creator herself practiced, because the infant is consuming less breast milk relative to body weight and has more mature gut enzyme activity.

The creator's enthusiasm is understandable. But "not detectable in most samples" and "safe" occupy different categories of scientific certainty, and conflating them in a video targeting breastfeeding mothers with 26,000 views carries real consequences.