Tirzepatide is a long-acting GIP (glucose-dependent insulinotropic polypeptide) receptor and GLP-1 (glucagon-like peptide-1) receptor agonist that increases insulin sensitivity and secretion, suppresses glucagon secretion, and slows gastric emptying.
July 2025 please be aware of the risk of pancreatitis GLP-1 receptor agonists: MHRA to study possible side effects after acute pancreatitis cases | The BMJ “Data from the Medicines and Healthcare Products Regulatory Agency (MHRA) show that hundreds of cases of acute and chronic pancreatitis, including 10 deaths, have been reported in people taking the drugs, which are used to treat weight loss and diabetes by mimicking a natural hormone released after eating, although it is not certain that the drugs are the cause.”
June 2025 the MHRA recommended that all women taking “skinny jabs” should use effective contraception.
“Effective contraception includes oral (the pill) and non-oral (the implant, coil or condoms) forms of contraception. However, Mounjaro may reduce the effectiveness of oral contraceptives in those who are overweight. Therefore, those taking Mounjaro who are overweight and are using an oral form of contraception are advised to also use a non-oral form of contraception. This only applies to those taking Mounjaro and is especially important for the four weeks after starting Mounjaro and after any dose increase”
Tirzepatide is used to treat Type 2 diabetes mellitus as monotherapy (if metformin is inappropriate), or in combination with other antidiabetic drugs (including insulin) if existing treatment fails to achieve adequate glycaemic control. It is also used in the treatment of obesity by weekly subcutaneous administration.
No information is available on the clinical use of tirzepatide during breastfeeding. Because tirzepatide is a large peptide molecule with a molecular weight of 4814 Da, the amount in milk is likely to be low and absorption is unlikely because it is probably partially destroyed in the infant’s gastrointestinal tract. Until more data become available, tirzepatide should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant. (LactMed).
Due to its protein nature, it is inactivated in the gastrointestinal tract and is not absorbed (oral bioavailability is practically nil), which makes it difficult or impossible for it to pass into the infant’s plasma from ingested breast milk, except in premature infants and in the immediate neonatal period, where there may be greater intestinal permeability. (E-lactancia).
While caution is still necessary without confirmatory data, it is unlikely to be present in large quantities in the milk compartment (Hale )
See also https://www.infantrisk.com/content/weight-loss-lactation
Weight Loss in Lactation | InfantRisk Center
Hale and Krutsch (Infantrisk pharmacists express concern on the use of weight loss medications and breastfeeding due to inadequate consumption of nutrients.
“Concerns have been expressed about how the pharmacodynamics of GLP-1 agonists such as tirzepatide or semaglutide could impact the nutritional constituents of milk. These drugs are analogs of natural GLP-1 with small modifications to slow their degradation by the DPP-4 enzyme. However, lactation, in general, is expected to occur during a catabolic physiological state – GLP-1 agonists catalyze the catabolism to encourage weight loss. As long as the mother has sufficient weight to lose, the nutrient profile of milk would likely be similar if compared to a diet producing equivalent weight loss. If a mother is reducing caloric intake for any reason, we recommend a postnatal vitamin and attention to consuming enough calories to meet the elevated nutrient needs required during lactation”.
June 2025 the MHRA recommended that all women taking “skinny jabs” should use effective contraception.
“Effective contraception includes oral (the pill) and non-oral (the implant, coil or condoms) forms of contraception. However, Mounjaro may reduce the effectiveness of oral contraceptives in those who are overweight. Therefore, those taking Mounjaro who are overweight and are using an oral form of contraception are advised to also use a non-oral form of contraception. This only applies to those taking Mounjaro and is especially important for the four weeks after starting Mounjaro and after any dose increase”
Other sources of information
NICE TA 1026 Tirzepatide for managing overweight and obesity . https://www.nice.org.uk/guidance/ta1026
See also Semaglutide and Breastfeeding https://breastfeeding-and-medication.co.uk/fact-sheet/semaglutide-and-breastfeeding
Liraglutide and Breastfeeding https://breastfeeding-and-medication.co.uk/fact-sheet/liraglutide-saxenda-and-breastfeeding