Can weight loss medication interfere with your birth control?

The likes of Wegovy and Mounjaro are transforming the way we approach obesity treatment - but the way they work is actually quite simple.

They slow down the absorption of food in your body, which helps to regulate your appetite and reduce your calorie intake. When combined with a balanced diet and regular exercise, this can lead to weight loss over time.

But it has been suggested that when you take weight loss medication, that same mechanism could also slow the absorption of oral contraceptives, reducing their effectiveness. Let’s look at the science behind the suggestion.

Why might weight loss medication affect birth control?

Although there has been limited research into this topic, it’s certainly a possibility. 

The Patient Information Leaflets for Wegovy and Mounjaro mention it as a potential clinical interaction, with one literature review finding that tirzepatide (the active ingredient in Mounjaro) had a greater impact on the absorption of oral contraceptives than other GLP-1 agonist weight loss medications.

There isn’t a universally-accepted reason why weight loss medication might affect birth control medication, but there are a few theories:

• Maintaining a healthy weight also helps to keep your hormones balanced, which gives women a greater chance of getting pregnant - rather than your birth control medication not working as it should.

• Two of the potential side effects of Mounjaro and Wegovy are vomiting and diarrhoea. Both of these could potentially make birth control medication less effective.

• Another possibility is that since weight loss medications slow down the absorption of food then they could do the same to birth control pills, reducing their effectiveness.

How can I minimise the risk?

Switch contraceptive method

Clinicians recommend using a barrier method of contraception (e.g. a condom) while taking Mounjaro. You can do this instead of an oral contraceptive method, or use both of them together.

Alternatively, you could consider switching to a non-oral contraceptive method for 4 weeks after starting treatment or for 4 weeks after each increase in dose.

Speak with a clinician

If you’re still concerned about the medication interfering with your birth control, speak to a clinician. They’ll be able to give you personalised advice based on your own situation and quash any concerns you might have.

The numan take

Although there’s a chance that weight loss medication could interfere with your birth control, there are steps you can take to reduce the risk, such as using a condom instead of a pill. But you should speak with a clinician to figure out the best option for you.