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Medicine guide

Clomifene (Clomid): ovulation induction tablets explained

Clomifene is a fertility tablet that encourages the ovaries to release an egg in women who do not ovulate regularly or at all. It is taken for five days at the start of a cycle, usually for up to six cycles, with a blood test to check whether ovulation is happening. The information here follows NHS guidance and hospital patient leaflets.

Last checked: 2026-10-03

Key facts

At a glance.

  • Purpose

    Stimulates the ovaries to produce eggs, in women who do not ovulate regularly or cannot ovulate at all.

  • Usual pattern

    Standard dose of 50mg once a day for 5 days, on days 2 to 6 of the menstrual cycle, per the NHS trust leaflet.

  • Cycle limit

    Usually prescribed for 6 cycles; longer is not advised because of reduced effectiveness and increased risks.

  • Monitoring

    A day 21 progesterone blood test checks whether ovulation occurred.

  • Twins

    Up to 10% of women who conceive on clomifene have twins; fewer than 1 in 1,000 have triplets or more.

  • Vision

    Blurred or yellow-tinged vision means stopping and seeking medical advice.

What clomifene does

Clomifene is a fertility drug that works by stimulating the ovaries to produce eggs. The NHS says it encourages the monthly release of an egg in women who do not ovulate regularly or cannot ovulate at all. It is a prescription medicine.

The NHS also notes that medicine that stimulates the ovaries is not recommended for women with unexplained infertility, because it has not been found to increase their chances of getting pregnant.

Who it is for and weight considerations

A hospital patient leaflet from an NHS trust describes clomifene as for women seeking fertility treatment, with results best when body mass index is ideally between 19 and 30. Those with a BMI above 35 are advised to lose weight first. This is guidance from one trust; your own clinic will set its criteria.

How a cycle works

The standard dose described is 50mg once daily for 5 consecutive days, starting on day 2 of the menstrual cycle and ending on day 6, at the same time each day.

A blood test on day 21 measures progesterone. A level of 14 nmol/l suggests that ovulation has happened; a lower level suggests it has not, which may prompt a dose increase. If your period is more than a week late, take a pregnancy test.

How many cycles are used

The leaflet says clomifene is usually prescribed for 6 cycles. Treatment beyond that is not recommended because effectiveness falls and the risks of endometrial thinning and ovarian cancer rise. If pregnancy has not happened after the planned cycles, the next step is a review with the fertility team to discuss options.

Side effects

The leaflet lists headaches, breast tenderness, dizziness, abdominal pain, low mood, rashes, hot flushes, ovarian cysts, weight gain, mood swings, nausea, vomiting and painful periods.

Blurring of vision or a yellow colouration of vision requires stopping the medicine and seeking medical advice.

  • Stop and get advice for any visual disturbance.

  • Tell your clinic about severe abdominal pain or swelling.

  • Report suspected side effects through the Yellow Card scheme.

Twins and multiple pregnancy

Up to 10% of women who conceive with clomifene have twins, and fewer than 1 in 1,000 have triplets or quadruplets.

Alternatives and related treatments

Other ovulation-stimulating options exist, including letrozole used under specialist supervision for PMOS, and assisted conception such as IUI or IVF. These are described in our guides to fertility treatment. Your specialist can explain which fits your situation.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • How many cycles of clomifene are normally used?

    The patient leaflet says it is usually prescribed for 6 cycles. Longer courses are not recommended because effectiveness falls and some risks rise.

  • When in the cycle is it taken?

    50mg once a day for 5 days, on days 2 to 6 of the menstrual cycle, at the same time each day, in the standard pattern described.

  • How do doctors check that it has worked?

    With a blood test for progesterone on day 21 of the cycle. A level of 14 nmol/l suggests ovulation; lower values suggest it has not occurred.

  • What are the chances of twins?

    Up to 10% of women who conceive on clomifene have twins, and fewer than 1 in 1,000 have triplets or quadruplets.

  • What should I do if my vision changes?

    Stop taking it and seek medical advice. Blurring or yellow colouration of vision is a recognised side effect.

  • Does body weight matter?

    The leaflet says results are best with a BMI of 19 to 30, and women with a BMI over 35 are advised to lose weight first.

  • When should I take a pregnancy test?

    If your period is more than a week late.

  • Is it suitable for unexplained infertility?

    The NHS says medicine to stimulate the ovaries is not recommended for unexplained infertility because it has not been shown to improve the chance of pregnancy.

  • What are the common side effects?

    Headaches, breast tenderness, dizziness, abdominal pain, mood changes, hot flushes, nausea, ovarian cysts and weight gain are among those listed.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-03, next review 2027-10-03.

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