Clomiphene (Clomid): how it works, experiences and side effects

Clomiphene, known in the Netherlands as Clomid or clomiphene citrate, has been the best known drug for inducing ovulation for more than 50 years. You usually take one 50 mg tablet for 5 days in a row, starting around day 3 of your cycle. Roughly 70 to 80 percent of women ovulate on it.

There is a catch that few patient folders mention: clomiphene can induce ovulation and thin your womb lining at the same time. Ovulating is therefore not the same as conceiving, and that difference explains a lot of frustration.

What is clomiphene and how does it work?

Clomiphene blocks oestrogen receptors in your hypothalamus. Your brain briefly concludes there is too little oestrogen and releases more FSH and LH. That extra FSH drives a follicle in your ovary to grow, and ovulation follows at the end of that growth.

So the drug does not make hormones. It nudges your own system, which explains why it works mainly in women whose signalling falters, as in PCOS, and much less when the ovarian reserve is depleted.

That same receptor blockade also acts on your womb lining and your cervical mucus. That is the downside we come to shortly.

The clomiphene schedule: which day do you start?

Almost every hospital protocol starts on cycle day 3, 4 or 5 and runs for 5 days. If you have no spontaneous period, your doctor induces one first with a progestogen. If the response is insufficient, the dose is raised in a following cycle.

These schedules come from Dutch hospital protocols and the Farmacotherapeutisch Kompas. The limit of about 6 ovulatory cycles exists because the chance of pregnancy flattens sharply after that, not because the drug becomes dangerous.

Clomiphene experiences: what do users report?

The stories are strikingly two-sided. The practical side is easy: 5 tablets, no injections, all at home. The emotional side is heavier, because every cycle has a result and the side effects land in exactly those tense weeks.

What comes back positively:

• Ovulation returning after years of absence
• A short 5 day course with no injections
• A clear rhythm and fixed check points, which gives something to hold on to
• Relatively low cost compared with other routes

What women find difficult:

• Hot flushes, sometimes strong, during and shortly after the course
• Mood swings and a short fuse
• A bloated belly and tender ovaries around ovulation
• Drier cervical mucus, which women often notice themselves
• Headache and poorer sleep

Picture two women of 29 with PCOS who both start on 50 mg. One ovulates in cycle one and is pregnant by cycle three. The other ovulates neatly on the scan, with a progesterone of 38 nmol/l around day 21, but does not conceive across four cycles. In her case the lining turns out to be thin around ovulation. The same result on paper, a different story.

Side effects of clomiphene

The side effects reported most are hot flushes, mood swings, bloating, tender breasts and headache. They relate to the temporary oestrogen shortage your brain experiences, and usually fade shortly after the course.

What you should take seriously are visual symptoms: blurred vision, flashes of light or spots. That is rare, but it is a reason to stop and contact your doctor. Ovarian cysts also occur, usually resolving on their own, and sometimes that is a reason to skip a cycle.

With ovulation induction the chance of a multiple pregnancy sits around 10 percent, nearly always twins. That is why follicle monitoring by ultrasound belongs with it, certainly in the first cycle at a new dose.

What are the chances of pregnancy?

Roughly 70 to 80 percent of women ovulate on clomiphene, and about half of them conceive across several cycles. That gap between ovulating and conceiving is the most important number in this whole article.

A Cochrane review of clomiphene and anti-oestrogens in PCOS confirmed that the drug clearly raises the chance of ovulation compared with placebo (PMID 19821295). Translating that into live births proved less straightforward, precisely because of the effects on lining and mucus.

The large NEJM trial by Legro in 2014 compared clomiphene directly with letrozole in women with PCOS and found more live births in the letrozole group (PMID 25006718). That is why letrozole is now first choice for PCOS in many Dutch clinics. Read more at letrozole experiences for PCOS and fertility.

Which values are tracked during a clomiphene course?

An ultrasound of follicle growth is the basis, but blood values fill in the picture. Progesterone around day 21, or about 7 days after the presumed ovulation, shows whether ovulation really happened. A clearly raised value fits with ovulation.

The starting position matters too. AMH says something about your ovarian reserve, LH and FSH about the signalling, and TSH and prolactin rule out other causes of absent ovulation.

You can have your progesterone tested to confirm ovulation, with an assessment by a BIG-registered doctor. Our explanation of confirming ovulation with a blood test and the progesterone reference values table per cycle phase help you read the result. For the broader picture, see fertility testing in women.

Alternatives to clomiphene

If clomiphene does not work, or you tolerate it poorly, there are several next steps. Which one fits depends on why your ovulation is absent.

• Letrozole, first choice for PCOS in many clinics
• Gonadotrophin injections, with more intensive monitoring
• With PCOS, lifestyle and insulin sensitivity too, see PCOS testing: which hormones and blood values
• A progestogen such as Duphaston when the goal is a regular bleed first rather than a pregnancy

That last point deserves emphasis. A progestogen makes your cycle more regular, but does not induce ovulation. When you are trying to conceive, that is a fundamentally different drug for a fundamentally different goal.

Frequently asked questions

Which day do you start clomiphene?

Usually on cycle day 3, 4 or 5, counted from the first day of your period. You then take it for 5 days in a row. Some protocols choose day 5 to 9. Follow the schedule from your own clinic.

When is ovulation after clomiphene?

For most women ovulation follows 5 to 10 days after the last tablet. Starting on day 3, that often lands somewhere between day 12 and day 17. An ultrasound pinpoints it more precisely than an ovulation test.

How many cycles can you use clomiphene?

Usual practice is a maximum of about 6 cycles in which you actually ovulate. If you have not conceived by then, another route is usually more useful than continuing. That is a conversation with your gynaecologist.

Can you buy clomiphene without a prescription?

No, and that is just as well. Without an ultrasound you cannot tell whether you are over-responding or not responding, and the risk of multiples and cysts needs supervision. Online offers without a prescription are unreliable.

Does clomiphene work without PCOS?

It works best in women who ovulate rarely or not at all, of whom PCOS is the largest group. If you already ovulate normally, the gain is small and side effects dominate. Your doctor weighs that up.

Clomiphene is an honest drug: cheap, well studied and effective at what it promises, which is inducing ovulation. Keep the distinction between ovulating and conceiving sharp in your own mind, and after three ovulatory cycles without a pregnancy, ask directly what the next step is. Asking costs nothing and often saves months.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Farmacotherapeutisch Kompas. Clomifene. Accessed 2026.
• Thuisarts.nl. I have polycystic ovary syndrome (PCOS) and want to become pregnant. Accessed 2026.
• Brown J, Farquhar C, Beck J, Boothroyd C, Hughes E. Clomiphene and anti-oestrogens for ovulation induction in PCOS. Cochrane Database of Systematic Reviews, 2009. PMID 19821295.
• Legro RS, et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. New England Journal of Medicine, 2014. PMID 25006718.
• Ovulation triggers in anovulatory women undergoing ovulation induction. Cochrane Database of Systematic Reviews, 2014. PMID 24482059.