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What to Expect When Taking Letrozole

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

If you aren’t successfully ovulating, or you need to induce ovulation for fertility treatments or to increase your chances of conceiving, one of the medications your doctor may choose to prescribe (or that you can discuss with them) is letrozole (also known as the brand name Femara).

Especially if this is new to you, you may have a lot of questions about ovulation induction as well as why this particular drug is recommended by many providers! Fortunately, when you have questions, we have answers. 

What to Expect When Taking Letrozole

Letrozole is a medication to help with inducing ovulation.

What is letrozole, and why take it? 

Letrozole belongs to the class of drugs called aromatase inhibitors, meaning they block the action of an enzyme necessary for estrogen production. Letrozole was originally discovered and used as a breast cancer drug, but blocking estrogen production turns out to be really helpful for ovulation induction as well! 

So helpful, in fact, that the International PCOS Network recommends letrozole as the first-line treatment for infertility secondary to PCOS. Even if you don’t have PCOS, it can also be helpful in inducing ovulation for those with endometriosis, other pelvic factor infertility, older TTC patients, and to help overcome mild male factor infertility. 

Letrozole is often compared to Clomid, another popular, older ovulation induction drug. It’s considered a better option for people with PCOS than Clomid, and it results in fewer instances of multiple pregnancies, which is a common side effect of Clomid. It also doesn’t build up in the body the same way that Clomid does, so people often experience fewer side effects with letrozole. 

How does letrozole work? 

Letrozole induces ovulation by binding to and blocking an enzyme that’s involved in the pathway to make estrogen. Normally, this enzyme converts testosterone to estradiol (a form of estrogen), but when blocked by letrozole, it can’t make any estradiol. 

Because there’s no estradiol being produced, your body assumes this means you haven’t ovulated yet, and begins to make FSH, kick-starting the process to ovulation after letrozole

Logistically, this means your doctor will usually recommend you take letrozole sometime in the beginning of your menstrual cycle, for around 5 days.  Dosage is usually around 2.5-5 mg per day, but doses up to 12.5 mg have been used and proven safe. 

Does letrozole affect ovulation test? Depending on what day you start treatment, you’ll then want to time intercourse when you’re most likely to be ovulating. The best way to do this is with LH tests like Proov Predict, which will give you the most precise information about your individual cycle and when you’re likely to be ovulating. If you’re using other fertility treatments, your doctor may wish to do an ultrasound as well to time those. 

What to Expect When Taking Letrozole

To know what day to start treatment and to know when to time intercourse, you'll want to use an LH test like Proov Predict.

What results can be expected? 

If you’re TTC and using letrozole, of course you’re hoping to conceive right away, and many people do! Even though the chances of letrozole working first time may be good, it’s important to keep in mind though that even the best ovulation induction drugs don’t work for everyone, and other infertility factors may still cause challenges (like male factor infertility or increased maternal age). 

Many studies from 2006-2012 found that ovulation rates per cycle with letrozole ranged from 60-86%, and the same studies saw pregnancy rates per cycle from 9-44%. While that may seem relatively low, keep in mind that it’s per cycle, and it’s common to take letrozole for several cycles before conceiving. The pregnancy rates are also higher than with clomid (7-26%). 

For your best chances at conceiving, you may want to follow up with your doctor to confirm you’re ovulating and ensure letrozole is working right for you.

What to Expect When Taking Letrozole

You may want to follow up with your doctor to confirm you're ovulating and ensure letrozole is working right for you.

What are the common side effects? 

While you should definitely talk to your provider about your personal medical history and chances of side effects, letrozole is generally well-tolerated, which is one of the reasons it’s becoming preferred over Clomid. 

Still, there are some common side effects, which can include headaches, hot flashes, bloating and cramping, mood swings, anxiety, and fatigue. Many of the reported side effects do come from cases of people being treated for breast cancer, not ovulation induction, so it’s reasonable to expect fewer side effects when taking letrozole for a shorter amount of time. 

Fortunately, letrozole has no impact on the uterine lining (unlike Clomid, which often thins it, complicating implantation), and there aren’t any restrictions on whether or not you can take it with food, or with what foods. 

If you’re TTC and need a little assistance with ovulation induction, you may want to talk to your doctor about letrozole/Femara! They can help you figure out what’s best for you. 

Have questions? Email us!