Weight loss drugs like Wegovy, Ozempic, and Mounjaro are now widely prescribed across the UK. Originally developed for managing type 2 diabetes, they’re increasingly used to support weight loss—especially for those who have a higher BMI and polycystic ovary syndrome (PCOS) or those advised to reduce their BMI before starting fertility treatment.
But what impact do these medications have on fertility? Are they safe to take when trying to conceive? And if they’re not, what are the alternatives?
Higher body weight can affect fertility in several ways. A raised BMI can disrupt the hormones that control ovulation, making periods irregular or absent altogether. It may also reduce how the body responds to fertility drugs, which can affect how the ovaries respond to medication during IVF.
In people with testes, a higher BMI can reduce sperm count and motility, while also affecting hormone balance.
There are also treatment access considerations:
These limits are based on clinical safety. A higher BMI can increase risks during sedation, the egg collection procedure and pregnancy.
In the UK, there are several licensed GLP-1 medicines including semaglutide (sold under the brand names Wegovy, Ozempic and Rybelsus), tirzepatide (Mounjaro) and liraglutide (sold under various brand names). “Licensed” means they have been assessed carefully by the UK medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), and approved as safe and effective for certain uses, outlined in the table below.
GLP-1s are medicines licensed to treat specific medical disorders and should only be used if you are overweight or diabetic, and not if you want to lose weight for aesthetic or cosmetic purposes.
The most common weight loss drugs in the UK are:
All three drug mimic hormones that help regulate appetite, digestion. Mounjaro also acts on the signalling system that controls blood sugar levels and insulin sensitivity. Taken once a week as an injection, they:
They can support gradual weight loss over several months and may lead to improvements in ovulation and menstrual regularity, especially in those with PCOS. Some research suggests they may help restore cycles in people who were previously not ovulating at all.
The Medicines and Healthcare products agency (MHRA), have recently (June 2025), released the following guidance:
No. These medications are not considered safe to use when trying to conceive, either naturally or via IVF, in pregnancy or breast feeding.
There’s a lack of long-term safety data for use in people undergoing fertility treatment or in pregnancy. Animal studies have shown potential risks to early development, and human studies are limited. Because of this, the current recommendation is to stop taking weight loss medication at least eight weeks before starting fertility drugs or attempting to conceive*.
This is at least 1 month for Mounjaro, and at least 2 months for Wegovy, Ozempic, and Rybelsus.
This period after stopping taking the medication is called the ‘wash out’ window, in which your body gets rid of any remaining drugs in your system. Following this guidance ensures accurate hormone testing and avoids any potential interactions with fertility medication.
If you’ve been prescribed a weight loss drug and are preparing for fertility treatment, it can be difficult to maintain weight loss momentum during the ‘washout’ window. But there are safe and effective alternatives that can help you stay on track without medication:
It’s important to avoid crash dieting or extreme restrictions, especially just before or during IVF. These can do more harm than good, potentially affecting hormone levels.
Possibly. For some individuals, particularly those with PCOS or insulin resistance, GLP-1 and GIP/GLP-1 medications may support hormonal regulation and restore ovulation. For others, the benefit may be primarily related to overall weight loss.
However, these drugs are not currently licensed as fertility treatments, and their use should be managed carefully in the context of your reproductive goals.
Speak to your GP or fertility specialist for personalised advice based on your medical history and treatment plan. If you're planning IVF, it's best to bring up any medication use early, so your care can be tailored safely around your goals.
*At the time of writing (July 2025) this was the guidance provided by the Medicines and Healthcare products agency (MHRA).