Ozempic while breastfeeding: what the evidence actually says

What did @getshapely actually say?

Dr. Zaghi cited the NIH's LactMed database to argue that semaglutide is unlikely to harm breastfed infants because it is a large molecule with low milk transfer and poor oral absorption. His conclusion was responsible: he recommended against using Ozempic while breastfeeding, calling it the position of "most weight loss specialists." Credit where it's due, the video ends in the right place. But the reasoning he used to get there deserves a closer look.

He walked viewers through semaglutide's pharmacokinetic properties: molecular weight over 4,000 daltons, greater than 99% protein binding, and estimated oral bioavailability of 0.4 to 1% from breast milk. These are real numbers pulled from real sources. He also acknowledged there are zero clinical trials on semaglutide use during breastfeeding. That transparency is not common in telehealth content aimed at postpartum audiences on TikTok.

Does the science back this up?

The pharmacokinetic logic is sound but incomplete. Large molecules with high protein binding do tend to transfer poorly into breast milk, and the oral bioavailability estimate he cited is consistent with what LactMed reports. However, using physicochemical properties to infer infant safety is an extrapolation, not evidence. It works for some drugs and fails badly for others.

Semaglutide's mechanism of action involves GLP-1 receptor agonism, and GLP-1 receptors are expressed in the developing gut and pancreas of neonates. Whether trace exposures matter during that window is genuinely unknown. The LactMed entry Dr. Zaghi referenced does state the drug is "unlikely to adversely affect a breastfed infant," but that language reflects educated inference, not clinical data. A 2023 review by Benyamin et al. in Breastfeeding Medicine noted that the entire GLP-1 agonist class lacks lactation safety data and called the evidence base "insufficient for clinical guidance." The FDA labeling for semaglutide states it should be used during lactation only if the potential benefit justifies the potential risk, which is not the same as saying it is probably fine.

What did they get wrong (or right)?

The molecular weight figure he cited deserves a small correction: semaglutide's molecular weight is approximately 4,114 daltons, so "over 4,000" is accurate. The protein binding figure above 99% is also consistent with published pharmacokinetic data from Marbury et al. (2021, Clinical Pharmacokinetics). Those details check out.

Where the video skips a step is in the implicit framing that low milk transfer equals low risk. That logic assumes the infant gut behaves like an adult gut, which it does not in the neonatal period. Intestinal permeability is higher in newborns, and some large peptides that would be destroyed in adult digestion may be absorbed at higher rates in infants. This is not settled science, but it is a known limitation of the "it's a big molecule" argument that was not mentioned. Also, the 0.4 to 1% oral absorption figure comes from extrapolation, not from studies in breastfed infants. Presenting it with that level of confidence without that caveat is a small but meaningful omission for a video tagged with "newborn."

What should you actually know?

If you are breastfeeding and considering semaglutide or any GLP-1 agonist for postpartum weight loss, the honest answer is that nobody knows if it is safe for your infant. The absence of harm in studies is not the same as evidence of safety, and there are no studies here at all. The recommendation to avoid these medications while breastfeeding is the correct one, and Dr. Zaghi gave it.

There are additional concerns the video did not raise. Semaglutide suppresses appetite significantly, and adequate caloric intake is already a challenge for many breastfeeding people. Caloric restriction during lactation can reduce milk supply and affect milk composition. A 2022 paper by Stuebe et al. in Obstetrics and Gynecology noted that aggressive postpartum weight loss interventions can compromise lactation outcomes independent of drug exposure. That context matters when a platform is actively marketing weight loss services to people tagged as postpartum in the video's own hashtags.

Use LactMed as a starting point, not a final answer. Talk to a lactation consultant and your OB before any weight loss medication postpartum.