The Truth About Breastfeeding and GLP-1s

Ozempic, Wegovy, Mounjaro and the question many postpartum mothers are quietly contemplating

The GLP-1 medications have gone from a diabetes clinic to the centre of every conversation about weight and many postpartum mothers are being swept up in it like everyone else. So the question lands in my inbox more and more often, usually carefully, usually from a mother who has been made to feel her body is a problem to be solved. "Is it safe to take one of these while I'm breastfeeding?"

So let me give you the version grounded in what the research actually shows. Where the evidence is solid, where it quietly runs outand what almost nobody is talking about.

First, what these drugs even are

Let's start with the dictionary, because it tells you something before we go anywhere near the science.

Semaglutide: "A drug that selectively binds to and activates cell receptors for glucagon-like peptide 1, acting to stimulate insulin secretion and decrease glucagon secretion, and that is administered orally or by injection for the management of type 2 diabetes."*

Merriam-Webster Medical Dictionary, 2026 [1]

*Marketed as Ozempic, Rybelsus and Wegovy. Now widely used, on and off label, for weight loss.

Notice what the definition leads with. Type 2 diabetes. The weight loss is the footnote. That's not an accident, it's the history.

GLP-1 stands for glucagon-like peptide-1, a hormone your gut releases after you eat. It nudges insulin up, glucagon down, slows the stomach and tells your brain you are full and the science here genuinely is old. The hormone was characterised back in the 1980s, when researchers mapped the proglucagon sequence it comes from [2]. But the medicines are much younger than that; the first GLP-1 drug, exenatide, was developed from a compound found in the venom of the Gila monster (one of my son's favourite animals!), a desert lizard and it was not approved until 2005, for type 2 diabetes [3]. Liraglutide followed in 2010 and semaglutide, the one behind Ozempic and Wegovy, arrived for diabetes in 2017 and for weight loss in 2021 [3]. So if you have read that these have been around since the eighties, that is half right. The hormone, yes. The injection, no.

The question you actually came here with

Does it pass into your milk and reach your baby?

The reassuring part starts with the molecule itself. Semaglutide is a large peptide, far bigger than the small molecules that cross easily into breastmilk and it travels through your blood almost entirely bound to a protein called albumin [4]. Large and tightly bound is exactly the profile that struggles to pass into milk and because it is a peptide - essentially a tiny protein - anything that did reach your baby's gut would largely be broken down before it could be absorbed. Two barriers, sitting one behind the other.

For once, the milk has actually been tested. In a 2024 study, eight nursing mothers using weekly semaglutide injections gave milk samples across a full day after their dose. The drug was not detectable in a single sample [5]. Working from a worst-case estimate, the researchers calculated the most a baby could receive at around 1.26% of the maternal dose, comfortably below the 10% threshold generally treated as a safety concern in breastfeeding [5]. The breastfed infants of mothers taking it showed no adverse effects [4].

An important distinction: injectable versus oral

The injectable forms of GLP-1s are the ones with the reassuring milk data. Some oral versions, such as Rybelsus, contain an absorption enhancer called salcaprozate sodium, which may enter milk and build up in an infant. On the current evidence, only the injectable forms should be considered during breastfeeding, not the oral tablet [4].

Where the evidence runs out

That aforementioned study is a single, small piece of work. Eight women. One drug. A short sampling window. It is genuinely reassuring on the narrow question of how much crosses into milk and it is nowhere near enough to call the matter settled. There is no long-term data on the babies who participated in the study. There is little to nothing of this quality on the other drugs in the class, like tirzepatide and crucially, "barely any reaches the baby" is not the same as "this is a good idea for a breastfeeding mother." Those are two completely different questions and the second one is the one being skipped.

The part almost nobody is discussing

Here is what I find genuinely worth pausing on. These drugs work by powerfully suppressing appetite. That is the entire point of them. Now think about what breastfeeding asks of a mother's body. Making milk burns roughly 500 extra calories a day and your stores of iron, calcium, B12 and more are already being drawn down and handed to your baby first. A medication whose job is to make you eat considerably less, layered on top of a body that is already giving so much away, raises real questions about maternal nutrition and potentially about milk supply, too. The researchers themselves named this, flagging that the effect on maternal nutrient intake and on the nutrient content of the milk remains unknown [5]. The conversation online is all about whether the drug reaches the baby. The question I would want answered is what happens to the mother who is barely eating while feeding one?

The risks of rapid weight loss when breastfeeding

There is a second, quieter concern here and it's one I've written about before because it matters so much. Your body fat is not inert storage. Over a lifetime it quietly accumulates persistent organic pollutants, or POPs, a family of stable, fat-loving chemicals such as old pesticides, PCBs and flame retardants, many of them banned precisely because they linger in the body for years [6]. They sit in your fat and, for the most part, stay put.

Rapid weight loss disturbs those POPs. When fat is broken down quickly, the pollutants stored inside it are released into your bloodstream and because breastmilk is rich in fat, they can pass into your milk. This is not speculation. In a study of lactating women, the concentration of these pollutants in breastmilk rose in step with how much weight the mother lost [7]. The researchers concluded that the benefits of breastfeeding still comfortably outweigh the risks, but with one important condition. That the weight loss is kept gradual, to around half a kilo, roughly a pound, a week [7].

GLP-1 medications are designed to do the opposite of gradual. Significant, fast weight loss is the entire selling point. So a breastfeeding mother losing weight rapidly on one of these is precisely the scenario that mobilises more of those stored pollutants into her milk. For me this is one of the clearest reasons the weight loss effects of these drugs deserve real thought in a nursing or pumping mother, quite separately from whether the drug molecule itself crosses over.

So where does that leave you?

If you have a genuine medical need for one of these drugs, this is a conversation for you and your doctor, weighing your health against limited but broadly reassuring transfer data and a lot of remaining unknowns. It is a real medical decision, and it is not mine to make for you.

What the evidence will not support is anyone telling you it is definitively, comprehensively safe to take while breastfeeding. The honest answer is that the milk transfer looks low and much else is simply not yet known.

A personal note, clearly marked as mine

Everything above is my best attempt at objectivity. This last part is not and I want to be transparent about the join. I feel very strongly about this topic and I will own that openly. Where one of these medications is treating genuine illness, type 2 diabetes, clinical obesity with real health consequences, I have no quarrel at all. That is medicine doing its job.

But the wider craze around them troubles me deeply and the popularity of them, aimed squarely at women, often postpartum women, frankly triggers me. We take a body that has just grown and birthed life and is now feeding an entire human being, a body that is depleted and healing and doing something extraordinary and we hand its owner a drug to make her want less, take up less, be less. I cannot pretend that sits comfortably with me. The fourth trimester and beyond should be a season of nourishing yourself, not shrinking.

So that is my bias, named out loud, so you can weigh it for exactly what it is. You are an intelligent woman. You get to take the evidence, take my honesty about where I stand and make your own decision from there.

References

1. Frontiers in Endocrinology. The discovery and development of liraglutide and semaglutide. 2019;10:155.

2. GLP-1 receptor agonists beyond diabetes management. eClinicalMedicine. 2024. doi:10.1016/j.eclinm.2024.103021.

3. Drugs and Lactation Database (LactMed). Semaglutide. Bethesda (MD): National Institute of Child Health and Human Development; 2006- [last revision 2026].

4. Diab H, Fuquay T, Datta P, et al. Subcutaneous semaglutide during breastfeeding: infant safety regarding drug transfer into human milk. Nutrients. 2024;16(17):2886.

5. Environmental contaminants in breast milk. PubMed PMID: 16399607.

6. Environmental organic pollutants in human milk before and after weight loss. Chemosphere. 2016. [verify full citation before publication]