Tirzepatide & breastfeeding: Is it safe?

Key Points:

• Emerging research is promising: New data suggests tirzepatide (Zepbound/Mounjaro) is largely undetectable in breast milk, though long-term safety studies are still ongoing.
• Your baby likely can't absorb it: Even if small amounts get into the milk, the baby's digestive system would likely break down the medication before it could be absorbed.
• Milk supply risks are indirect: The medication itself doesn't stop milk production, but eating too few calories or not drinking enough water while on it can lower your supply.

If you are struggling to lose weight after pregnancy or managing type 2 diabetes postpartum, you might be looking at tirzepatide – sold under the brand names Zepbound® and Mounjaro® – as a potential solution. These medications have incredible potential for weight loss and blood sugar management. But if you are nursing, you might be wondering: "Can I take tirzepatide while breastfeeding?"

The answer used to be a firm "no" due to a lack of data. However, new research is starting to change the conversation. While caution is still recommended, emerging evidence suggests that the risks may be lower than previously thought.

Here is an evidence-based breakdown of what we know so far about tirzepatide and breastfeeding, how it affects milk supply, and what you need to consider before making a decision.

Can you take tirzepatide while breastfeeding?

The official guidance from the FDA and most manufacturers has historically been to use caution or avoid these medications while nursing because there wasn't enough data to prove they were safe.

However, the scientific understanding is evolving.

According to the National Institutes of Health's LactMed database, tirzepatide is not expected to get into breast milk in large amounts. This is largely due to the physical properties of the drug itself. Furthermore, even if a tiny amount did transfer, it is unlikely to affect the infant because their body would destroy the drug during digestion.

Despite this reassuring profile, many healthcare providers prefer to err on the side of caution. They may recommend waiting until your baby is older and eating solid foods, or they may suggest alternative treatments with more long-term safety data.

Ultimately, the decision should be a conversation between you and your doctor, weighing your medical need for the medication against the theoretical risks to your baby.

Does tirzepatide pass into breast milk?

To understand how safe tirzepatide could be for breastfeeding parents, we have to look at the biology of how drugs transfer into milk. There are two main reasons why experts believe tirzepatide transfer is minimal:

1. Molecular size

Tirzepatide is a large peptide molecule. In pharmacology, the size of a molecule is measured in Daltons (Da). Small molecules (under 800 Da) can pass relatively easily from the mother's blood into breast milk.

Tirzepatide, however, has a molecular weight of approximately 4,813 Daltons. This large size makes it significantly harder for the drug to cross the biological barriers into your milk ducts. Current research suggests that because of this, the amount of drug present in milk is likely to be negligible or undetectable.

2. Oral bioavailability in infants

This is perhaps the strongest safety argument. Tirzepatide is a peptide (a protein-based chain). If you were to drink a vial of tirzepatide, it wouldn't work the way it does when it’s injected – your stomach acid and digestive enzymes would break it down just like they break down food proteins. That is why you have to take it as an injection.

The same logic applies to a breastfeeding infant. Even if trace amounts of tirzepatide made it into your breast milk, the baby would ingest it orally. The infant's gastrointestinal tract would likely degrade the peptide before it could be absorbed into their bloodstream to cause any effect.

Will Zepbound or Mounjaro affect my milk supply?

There is no evidence to suggest that tirzepatide directly targets the hormones responsible for milk production (prolactin and oxytocin). However, there is a significant indirect risk to your supply that you need to watch out for.

Monitoring caloric intake

Breastfeeding burns a lot of energy – typically an extra 450 to 500 calories per day. To maintain a healthy milk supply, you need to eat enough food to support both your body and your baby's growth.

Tirzepatide works by aggressively reducing your appetite. If you cut your calories too drastically while nursing, your body may respond by reducing milk production to conserve energy.

If you decide to take this medication while breastfeeding, it is crucial to work with a registered dietitian to ensure you are eating enough nutrient-dense food to keep your supply steady, even if you don't feel hungry.

“Being on a GLP-1 while breastfeeding is a delicate balance that necessitates expert supervision,” says Rita Faycurry, RD. “I always recommend partnering with a dietitian to ensure you’re getting the right nutrition to support both your health goals and your baby.”

Hydration is key

GLP-1 medications like tirzepatide can sometimes dull your sense of thirst or lead to mild dehydration. Since breast milk is mostly water, staying hydrated is non-negotiable for maintaining supply.

Does "pump and dump" work with tirzepatide?

Some mothers ask if they can take their weekly shot, "pump and dump" (discard) their milk for 24 hours, and then resume nursing. Unfortunately, this strategy does not work for tirzepatide.

"Pump and dump" is only effective for drugs that leave your system quickly (like alcohol). Tirzepatide has a half-life of approximately 5 days. This means it takes five days for just half of the dose to leave your body. It takes nearly a full month for the drug to be completely eliminated from your system.

Because the medication stays in your body at steady levels throughout the week, pumping and dumping offers no benefit and essentially wastes your milk.

Safe alternatives for weight loss while nursing

If you and your doctor decide that tirzepatide isn't the right choice for you right now, there are other safe ways to manage your weight and health postpartum.

• Metformin: For blood sugar management, metformin is widely considered safe during breastfeeding. Very little passes into milk, and it has been used safely for decades.
• Insulin: Insulin is the gold standard for diabetes safety during breastfeeding. The molecules are too large to pass into milk, and it is safe for the baby.
• Nutrition counseling: You don't have to navigate postpartum weight loss alone. A registered dietitian can help you create a plan that promotes safe, sustainable weight loss without compromising your milk supply.

Final thoughts

The conversation around tirzepatide and breastfeeding is shifting. While we still lack long-term human studies and more research is needed, the chemical properties of the drug – specifically its large size and poor oral absorption – suggest that the risk to a breastfed infant is likely very low.

However, "low risk" is not the same as "no risk." The decision to take Zepbound or Mounjaro while nursing should be made carefully. You have to balance the benefits of maternal weight loss and blood sugar control against the unknown long-term effects on the infant.

If you choose to use these medications, monitor your baby for any changes in feeding or growth, and prioritize your own nutrition to protect your milk supply.

Frequently Asked Questions

How long does tirzepatide stay in your system for breastfeeding?

Tirzepatide has a half-life of about 5 days, meaning it takes roughly 4 to 5 weeks to completely leave your system. Because it stays in your body so long, you cannot simply skip breastfeeding for a day or two after your shot.

Can Zepbound dry up my milk?

Zepbound does not chemically stop milk production, but it can lower your supply indirectly. If the medication causes you to eat too few calories or drink too little water, your body may produce less milk as a survival mechanism.

Can I take Ozempic while breastfeeding instead?

Ozempic (semaglutide) is similar to tirzepatide but is a slightly smaller molecule. Like tirzepatide, it is a peptide and has poor oral absorption in infants. Recent small studies have shown undetectable levels of semaglutide in breast milk, leading many experts to believe it is also likely safe, though caution is still advised.

The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.