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Clomid (Clomiphene) Side Effects and Risks

Mood Swings, Headaches, Bloating, and Twins


Updated June 02, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Clomid (clomiphene) side effects are mild for most people. However, as with any drug, you should be aware of the potential side effects before treatment. There are also some risks to clomiphene treatment, like the increased risk of having twins.

Clomiphene, sold under the brand names of Clomid and Serophene, tricks the body into thinking there’s not enough estrogen by blocking the estrogen receptors. This leads the body to release more GnRH, a hormone that leads the pituitary to release more FSH and LH. These hormones stimulate the ovaries and boost ovulation. 

Because most of the estrogen receptors are blocked, this leads to some of clomiphene’s side effects like headaches and vaginal dryness. Most of the other side effects are caused by the ovaries becoming slightly enlarged.

Important note! Not all possible side effects and risks are listed below. If you are experiencing severe side effects, unusual symptoms, or are concerned for any reason, contact your doctor. The information in this article does not replace consultation with a medical professional.

Hot Flashes

Woman having night sweats
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Hot flashes (or, in official 'doctor speak,' vasomotor flushes) are a common side effect of clomiphene, with 10% of women experiencing them in clinical studies.

When you’re having a hot flash, you may suddenly feel extremely warm, experience face flush, break out in a sweat, and have a more rapid heartbeat. After a hot flash, you might feel chilled (especially if you broke out in a sweat).

Hot flashes are also known as night sweats if they happen while you’re sleeping. A hot flash can be a bit unnerving the first time it happens, but it’s not a dangerous event -- just an uncomfortable one.

Bloating and Abdominal Discomfort

Woman with hands over abdomen
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Another very common clomiphene side effect is bloating and abdominal discomfort, occurring in about 5% of women.

During treatment, it may help to wear clothing that isn’t too tight around the waist. The bloated feelings should pass once your treatment cycle is over. Of course, if you experience more than moderate discomfort and cramps, call your doctor.

Weight Gain

Scale at zero
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Weight gain isn’t as common as bloating, with less than 1% of women reporting weight changes. But it’s a side effect that you hear often through the infertility grapevine. If the weight gain is connected to bloating, then your weight should go back to normal after treatment.

Mood Swings

Anxious woman.
Paul Bradbury / Getty Images

Mood swings are another side effect of clomiphene that in clinical studies didn’t appear as often as I’d imagine (less than 1% of women). But that’s difficult to believe, given how many women have told me the mood swings were the worst side effect.

Mood swings may mean feeling more emotionally sensitive, tearful, or even depressed or anxious, though infertility itself can bring on these feelings without drugs. It helps to be forgiving and gentle with yourself, and to practice good self-care during treatment.

Nausea and Dizziness

Woman feeling dizzy
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About 2% of women experienced nausea and vomiting while taking clomiphene. Taking the medication in the evening may help with this.

If the nausea is intense, or you have trouble keeping down food and fluids, be sure to report this to your doctor. Severe nausea can also be a sign of ovarian hyperstimulation syndrome, a rare but potentially dangerous side effect of fertility drugs.

Breast Tenderness

Woman with her hand over her chest
9nong / Shutterstock

Breast tenderness is another potential side effect of clomiphene, occurring in 2% of women during clinical trials.

This is another side effect that can have women wondering if they’re experiencing early pregnancy symptoms, but usually it’s just a drug side effect.

Abnormal Menstrual Bleeding

Panty liner on top of a red calendar
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Just over 1% of women in clinical trials reported spotting, or abnormal menstrual bleeding.

This can drive some women crazy, since they see spotting and think, “Oh, it’s implantation spotting!” But especially if you’re taking fertility drugs, the spotting in the middle of your cycle can be related just to the drugs and doesn’t necessarily indicate pregnancy.

If the spotting is accompanied by other symptoms, like abdominal pain, nausea and vomiting, or fever -- or something just doesn’t feel right -- contact your doctor.


Woman holding her head
Marili Forastieri / Getty Images

A little over 1% of women in clinical trials reported headaches. If you’re experiencing headaches, it may help to take the medication in the evening, instead of the morning, so you can sleep through them. (If your doctor told you to specifically take the medication in the morning, you should ask first.)

You should also be sure to get plenty of fluids, since mild dehydration can also lead to headaches.

Vaginal Dryness or Thick Cervical Mucus

Bottles of body oils
Thesaint / Stock.xchng

This is a frustrating potential side effect of clomiphene, as thick or absent cervical fluid can interfere with achieving pregnancy. Cervical mucus is needed to help transport the sperm into the cervix. If clomiphene causes thick cervical mucus, this can decrease the chances of getting pregnant.

You should let your doctor know if this happens during treatment. He can consider whether clomiphene is the right drug for you, or find a way to treat or bypass the problem (like with IUI treatment).

You may want to try using a sperm-friendly lubricant to make sex more comfortable.

Blurred Vision

A blurred highway road.
Rickyd / Shutterstock

A frightening, but usually not dangerous side effect of clomiphene, is blurred vision. It occurred in 1.5% of women during clinical trials. Blurred vision, seeing flashing lights, and seeing floaters may occur, especially at higher doses. The good news is that this side effect is typically temporary and goes away once you stop taking the drug.

If you experience vision changes, be sure to contact your doctor right away. The symptoms should go away once the medication is stopped. (And obviously, you should take care in driving or operating dangerous equipment if you do experience visual side effects.)

Risks of Clomid

While side effects are usually physical or emotional discomforts experienced while taking a drug, a drug's risks are what may occur beyond what you feel. With that said, here are the possible risks to clomid:

Twin or multiple pregnancy: The risk of getting pregnant with twins or more may be the most well-known risks of clomiphene. During clinical trials, 6.9% of pregnancies were twin pregnancies, 0.5% were triplets, 0.3% were quadruplets, and 0.1% were quintuplets. To reduce the chances of having twins, your doctor should always start you on the lowest dose first, 50 mg, before trying higher doses.

Ovarian Hyperstimulation Syndrome (OHSS): Usually mild with clomiphene treatment, but in rare cases, the severe form can occur. Without treatment, severe OHSS can be life threatening.

If you experience nausea, severe abdominal or pelvic pain, sudden weight gain, or severe bloating, contact your doctor immediately.

Irreversible vision disturbances: Extremely rare, only in those who continue treatment after vision disturbance began. In those who discontinued treatment, vision disturbance stopped after three days.

Ovarian cysts: Less than 1% of women will develop an ovarian cyst during treatment. The cyst is typically benign (not cancer), and it should go away on its own not long after the treatment cycle is over. If the cyst does not go away, the doctor should follow up and reevaluate. In rare cases, it may require surgical intervention.

Ovarian cancer: Some studies have found an increased risk of ovarian cancer if clomiphene is taken for a year or longer. It's unclear if this is caused by clomiphene or infertility itself.

More on fertility drugs and treatment:

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Clomid Drug Information Sheet. Sanofi-Aventis. Accessed February 24, 2009. http://products.sanofi-aventis.us/clomid/clomid.pdf

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