If you are not ovulating regularly, that alone can be the reason you have not conceived — and it is one of the more treatable causes of infertility. Ovulation induction means using medicine to encourage your ovaries to release an egg. This page explains what it involves, so you know what to expect before you come in.

What ovulation induction is for

Each month, one of your ovaries should release an egg. If that is not happening — or is happening only occasionally — there is no egg for sperm to fertilise.

You may not be ovulating regularly if your periods are:

  • Very irregular — unpredictable gaps between them
  • Absent for months at a time
  • Very infrequent — only a few times a year

The commonest reason for this is polycystic ovary syndrome (PCOS). Thyroid problems, raised prolactin levels, very low body weight and excessive exercise can also stop ovulation.

Before starting treatment

Ovulation induction is not the first thing we do. There are a few checks first, because treating the wrong problem wastes time — and time matters in fertility.

  • Confirming that you are not ovulating, usually with a blood test and your cycle history
  • Thyroid and prolactin blood tests, since both are treatable causes
  • Checking your tubes are open — there is no point stimulating an egg if it cannot meet sperm
  • A semen analysis for your partner — a male factor is present in a substantial proportion of couples, and it changes the plan entirely
  • Weight, blood pressure and blood sugar, particularly with PCOS

The medicines we use

Treatment starts with tablets, and moves to injections only if tablets do not work.

Letrozole — the usual first choice

Letrozole tablets are taken for a few days early in the cycle. It is now the preferred first-line treatment for women who are not ovulating, particularly with PCOS, because it produces more live births than the older alternatives and carries a lower chance of twins.1,2

Clomifene — used in selected patients

Clomifene citrate is the older tablet treatment and still has a place. I use it in selected patients, depending on availability and on the individual clinical picture.1

Gonadotrophins — second-line

If tablets do not produce ovulation, gonadotrophin injections are the next step. These stimulate the ovaries more directly and more strongly. They need closer monitoring, because the ovaries can over-respond.1,2

Monitoring during treatment

While you are on treatment you will have ultrasound scans to see how the follicles (the fluid-filled sacs that contain the eggs) are developing. This tells us whether the dose is right, when you are likely to ovulate, and whether too many follicles are growing.

Monitoring is not an optional extra. It is what keeps the treatment both effective and safe.

Every plan is different

There is no single protocol that suits everyone. The choice of medicine, the dose, how long we continue, and when to change approach all depend on your age, your weight, how long you have been trying, what your tubes and your partner's results show, and how your ovaries respond in the first cycle or two.

Your treatment will be individualised. If a friend or relative was given something different, that does not mean either of you is being treated wrongly.

What are the chances, and how long does it go on?

Most women who are going to ovulate on tablets do so within the first few cycles. Treatment is usually continued for a limited number of cycles, and then reviewed — if it is not working, continuing indefinitely is not the answer.

Success also depends on factors other than ovulation: your age above all, and whether there is anything else affecting fertility.

Risks to know about

  • Multiple pregnancy. Stimulating the ovaries raises the chance of twins. Twin pregnancies carry more risk for both mother and babies, which is one reason monitoring matters and doses are kept modest.
  • Ovarian hyperstimulation syndrome (OHSS). The ovaries over-respond and become swollen and painful. It is uncommon with tablets, more of a consideration with injections. Tell us promptly about severe abdominal pain, bloating, vomiting or breathlessness.
  • Side effects. Hot flushes, mood changes, headaches and abdominal discomfort are common and usually mild.

When we consider IUI or IVF

Ovulation induction is sometimes combined with intrauterine insemination (IUI), where prepared sperm is placed directly into the womb around the time of ovulation.

IVF is considered when ovulation induction has not succeeded after a reasonable trial, when the tubes are blocked, when there is a significant male factor, or when age means waiting is not in your favour.3

What you can do yourself

  • Reach a healthy weight. In PCOS, even a modest weight loss can restore ovulation on its own, and it improves how well the medicines work.1
  • Stop smoking, and keep alcohol low.
  • Start folic acid before you conceive — see our preconception care article.
  • Try not to let it take over. Fertility treatment is stressful. Say so, if it is getting hard.

When to come and see us

Please make an appointment if you have been trying for a year without success, or six months if you are over 35. Come sooner if your periods are very irregular or absent, if you have known PCOS or endometriosis, or if you have had previous pelvic surgery or infection.

The takeaway

If you are not ovulating, ovulation induction is a straightforward and often successful treatment. Tablets come first — letrozole in most cases, clomifene in some — and injections are the next step if needed. The plan is built around you rather than around a protocol, and the sooner we assess you, the more options you have.

References

  1. Teede HJ, Tay CT, Laven J, Dokras A, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Hum Reprod. 2023;38(9):1655–79. Available from: https://pubmed.ncbi.nlm.nih.gov/37580037/
  2. National Institute for Health and Care Excellence. Fertility problems: assessment and treatment (NG257) [Internet]. London: NICE; 2026 [cited 2026 Jul 22]. Available from: https://www.nice.org.uk/guidance/ng257
  3. NHS. Infertility — Treatment [Internet]. London: NHS; [cited 2026 Jul 22]. Available from: https://www.nhs.uk/conditions/infertility/treatment/