GLP-1 and breastfeeding

Why GLP-1 is contraindicated during breastfeeding

The European product information for Ozempic, Wegovy, Rybelsus, Mounjaro and Saxenda all states that the medicine must not be used during breastfeeding. The underlying reason is a combination of insufficient research in humans and demonstrated transfer into milk in animal studies.

There is also a second, clinically relevant argument: GLP-1 causes reduced appetite and weight loss in the mother. Unintentionally, this can lead to calorie deficits that inhibit milk production and lower the nutrient quality of the breast milk. Breastfeeding has an average additional calorie requirement of 450-500 kcal per day — a GLP-1 programme is fundamentally at odds with that.

Thirdly: infants are sensitive to even low doses of pharmacologically active peptides. Although GLP-1 in breast milk is probably largely broken down in the baby's digestive system, there are no human data that rule out that part of it nevertheless remains systemically active.

What the milk-transfer data say

For semaglutide, a measurable concentration of the medicine has been found in rat milk — around 3-12% of the plasma concentration. Comparable data exist for tirzepatide and liraglutide. In humans there has been virtually no direct research into this, so extrapolation from animal data remains the basis.

GLP-1 is a peptide and would theoretically be largely broken down in an infant's stomach — comparable to why GLP-1 does not work as a simple tablet (hence the injection or special tablet form). Yet this is no reason to ignore the contraindication: the certainty is simply not there.

Postpartum myths about stopping breastfeeding (such as 'it is out of your system in a few days') are not true for GLP-1. Because of the long half-life of semaglutide (~1 week) and tirzepatide (~5 days), it takes 5-6 weeks before the medicine has practically completely disappeared from the maternal plasma — and therefore from the milk.

Washout periods per GLP-1 medicine

Semaglutide (Ozempic, Wegovy, Rybelsus): half-life ~1 week. Stop breastfeeding during treatment, or stop GLP-1 and wait at least 5-6 weeks before breastfeeding again.

Tirzepatide (Mounjaro, Zepbound): half-life ~5 days. Wait at least 4-5 weeks after the last dose before breastfeeding can be resumed.

Liraglutide (Saxenda): half-life ~13 hours. Wait at least 5 days after the last dose. Because of its short half-life, liraglutide is in practice the 'least bad' GLP-1 for lactation — but it is still contraindicated according to EMA.

Oral semaglutide (Rybelsus): same half-life as the injections, so the same 5-6 week waiting period before resuming breastfeeding.

Losing weight while breastfeeding without medication

While breastfeeding, the body burns around 450-500 extra kcal per day for milk production. This means a healthy weight loss of 0.5-1 kg per month can be achieved without any disadvantage to the child. Losing weight too aggressively (>1 kg per week or <1800 kcal per day) is not recommended because of the risk of a drop in milk production.

Practical tips: enough protein (1.2-1.5 g per kg of body weight per day), enough fluids (2.5-3 litres per day), limit fast carbohydrates and choose vegetables and wholegrain products. 30 minutes of moderate exercise daily (walking with the pram) contributes without affecting milk production.

A dietitian with experience in lactation can draw up a personal plan. At Go Leaner we work with dietitians who are specifically familiar with postpartum weight loss within the safety of breastfeeding.

Weaning in order to start GLP-1

Some women with considerable excess weight and a medically urgent need to lose weight choose to wean early in order to start GLP-1. This is a personal decision in which medical, social and emotional factors play a part.

Practical route: discuss the consideration with your midwife or child health clinic (consultatiebureau), wean gradually over 2-4 weeks (one feed less per week), switch to formula feeding once breastfeeding has stopped. Then wait 1-2 weeks to stabilise hormonally, and start GLP-1 under the supervision of a BIG-registered doctor.

WHO guidelines recommend at least 6 months of breastfeeding and preferably up to 1-2 years. Stopping early for weight loss is medically acceptable but is rarely advised as the first option by child health clinics. An open conversation with a lactation consultant is valuable here.

After breastfeeding — when it is safe to start

Immediately after completely stopping breastfeeding you can safely start GLP-1. No 'waiting period' needs to be observed — milk production stops within a few days of the last feed, and GLP-1 has no rebound effect on lactation.

For women with postpartum weight retention, GLP-1 is often an effective solution. Studies show that average weight loss in postpartum women is comparable to the general population. One point of attention: ensure adequate iron and vitamin D supplementation if these have not yet recovered from the pregnancy.

When resuming contraception alongside GLP-1: take into account the interaction between GLP-1 and oral contraception during the titration phase (see our article on GLP-1 and pregnancy).

Go Leaner's advice on postpartum weight and family planning

At Go Leaner we regularly see women struggling with residual weight after pregnancy. At every intake, our BIG-registered doctors actively assess whether breastfeeding is still ongoing and, if so, how long it is still planned.

During active breastfeeding we do not start GLP-1. We discuss the options: nutrition coaching with gradual weight loss during breastfeeding, or a plan to start medication immediately after the intended end of breastfeeding.

In women with morbid obesity (BMI >40) and/or medical comorbidity where delay is risky, stopping breastfeeding earlier can be considered — always in consultation with the GP and child health clinic (consultatiebureau).