Letrozole vs Clomid for PCOS: what is different and what to ask your clinic
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If PCOS makes ovulation irregular or absent, you may hear two names at a fertility appointment: letrozole and Clomid (clomiphene citrate). Both may be used to encourage ovulation, but they are not interchangeable instructions you can follow at home. Which one is appropriate depends on your diagnosis, other fertility factors, availability and your clinician’s plan.
First, what problem are we trying to treat?
Ovulation induction aims to help an egg develop and be released. That can be useful if you are not ovulating regularly, but it does not address every possible reason conception is difficult. Before choosing a medicine, ask whether sperm factors, tubal issues and any other relevant conditions have been considered. The comparison below focuses on PCOS with anovulatory infertility and no other identified infertility factors, the group addressed by the international PCOS guideline.
How are the medicines different?
Letrozole is an aromatase inhibitor. It temporarily reduces oestrogen production, prompting hormonal signals that can support follicle development. Clomiphene acts on oestrogen signalling to stimulate the hormonal pathway leading to ovulation. Both are prescription medicines. Neither guarantees that an egg will be released or that a pregnancy will follow.
Which does the PCOS guideline favour?
The 2023 International Evidence-based Guideline for PCOS recommends letrozole as the first-line medicine for inducing ovulation in women with PCOS who have anovulatory infertility and no other infertility factors. In that defined group, the guideline recommends letrozole over clomiphene to improve ovulation, clinical pregnancy and live-birth outcomes. That is a population-level recommendation, not a prediction of your personal result.
Letrozole is used off-label for ovulation induction in many countries, and rules and availability vary. If your clinic proposes Clomid instead, ask why: your individual history, local prescribing rules and the clinic’s plan may all matter. Do not assume a different recommendation means your care is wrong.
What about monitoring and risks?
Ask how your team will check whether a follicle develops and whether ovulation occurs. Monitoring may include ultrasound or blood tests according to the protocol. The PCOS guideline notes that clomiphene increases the risk of multiple pregnancy, so clomiphene cycles may require ultrasound monitoring. With either medicine, contact your clinic if you have concerning symptoms, and never change the dose or start another cycle on your own.
Clomiphene can also cause side effects. MedlinePlus advises prompt medical contact for visual changes such as blurred vision, spots or flashes, as well as abdominal swelling or pain and breathing difficulty. Your prescriber should explain the specific side effects and safety instructions for whichever medicine you are offered.
Questions worth taking to the appointment
- Do my results show that I am not ovulating, and have other infertility factors been assessed?
- Why are you recommending letrozole or Clomid for me?
- Is letrozole available and permitted for ovulation induction where I am being treated?
- How will you monitor follicle development, ovulation and the risk of multiple pregnancy?
- What side effects mean I should call, and whom do I contact outside office hours?
- What is the plan if I do not ovulate, ovulate without conceiving or develop too many follicles?
- When will we review the approach rather than repeating the same treatment?
For many people with PCOS, the most useful question is not “Which tablet is stronger?” but “Why is this treatment the right next step for my circumstances, and how will we know whether it is working safely?” A good plan gives you an explanation, a monitoring strategy and a point at which to reassess.
This article is general information, not a prescription or dosing guide. Ovulation-induction medicines should be used only under a qualified clinician’s direction. Treatment choices may differ if other infertility factors are present.