Does Semaglutide Affect Fertility, and What Should You Do Before Trying to Conceive?

What the semaglutide trials measured — and what they didn't

The large phase-3 semaglutide weight-management trials, including STEP 1, published in the New England Journal of Medicine, were designed to measure body weight, cardiovascular markers and tolerability over 68 weeks. Fertility outcomes were not primary endpoints, and participants were required to use reliable contraception throughout, so the trials were never set up to detect an effect on conception rates one way or the other. That's not a scandal; it reflects standard practice for early-phase medicines research. What it does mean is that the absence of a signal in those trials cannot be read as proof that there is no effect: the data simply wasn't collected in a way that would reveal one. Anyone who tells you definitively that semaglutide either does or doesn't affect fertility is going beyond what the published evidence supports.

Animal reproductive studies conducted as part of the regulatory process showed embryo-foetal toxicity at doses comparable to human therapeutic levels, which is a significant part of why the MHRA takes the position it does on contraception and conception. That animal data doesn't automatically translate to humans, but regulators apply caution where gaps exist. The NHS semaglutide information page reflects this directly, advising women to avoid becoming pregnant while taking the medicine.

How weight change itself can alter reproductive hormones

This is where things get more nuanced, and genuinely useful to understand. Carrying excess weight affects sex hormone levels in both men and women. In women, obesity is associated with elevated oestrogen, disrupted menstrual cycles and a higher rate of conditions such as polycystic ovary syndrome (PCOS), all of which can suppress ovulation. Weight loss, including the kind seen with semaglutide treatment, can restore more regular cycles in some women, sometimes unexpectedly so. Several patients starting weight-loss treatment who assumed they were unlikely to conceive have found otherwise.

The practical implication is worth stating plainly: if you are sexually active and not planning a pregnancy, effective contraception matters from the very first dose. The improvement in fertility that weight loss can bring may arrive sooner than anyone anticipates. Our detailed page on how semaglutide may affect female fertility specifically covers this hormonal picture in more depth, and there is a separate page looking at semaglutide and male fertility for those asking that question.

The MHRA's position on contraception, conception and stopping treatment

The MHRA advises that women should use effective contraception during semaglutide treatment and for a period after stopping before trying to conceive. The exact washout period should be confirmed with your prescriber, since it depends on the half-life of the medicine and your individual circumstances, this is not a decision to make based on a webpage. What is clear from NHS England's guidance on weight-management injections is that these medicines are not recommended in pregnancy or while breastfeeding, and that planning ahead with your clinical team gives you the best options.

For women thinking about conception in the coming months or years, raising this explicitly at your consultation matters, not as an afterthought, but as a central part of whether and when treatment is appropriate. A prescriber can factor your timeline into any dose decisions and help you plan a sensible stop point. If you'd like to read more about the full picture around semaglutide during and after pregnancy, the Wegovy and pregnancy page covers that ground. For a broader view of how semaglutide interacts with the body beyond weight loss, the page on semaglutide and heart health is worth reading alongside this one.

What to do next if you're planning a family

Talk to your GP or prescriber before making any changes to your treatment. Stopping semaglutide without a plan is not necessarily the right move either, the timing matters, and a prescriber who knows your full picture can advise on the best approach. If you are currently taking semaglutide through another provider and want a clinical team that reviews your case at every repeat order, how nume works explains our approach. Every repeat prescription is clinically reassessed (not rubber-stamped) which creates a natural moment to flag changes in your circumstances, including family planning.

If you are not yet on treatment and are weighing up whether semaglutide is right for you given your reproductive plans, a free consultation is a low-commitment way to get a prescriber's view. The Wegovy overview page sets out what the treatment involves day to day. Once approved, the medicine is dispatched the same day and arrives by tracked DPD delivery the next working day in plain packaging, practical details that matter when you're managing something personal. Questions about eligibility and pricing can be found on the Wegovy pricing page, and a free consultation is where suitability is properly assessed.