Femara (letrozole) is a prescription brand-name medication. It’s approved by the Food and Drug Administration (FDA) to treat certain types of breast cancer in adult females* who’ve been through menopause.
Here are some fast facts about Femara:
- Active ingredient: letrozole
- Drug class: aromatase inhibitor
- Drug form: oral tablet
Like other drugs, Femara can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Femara, including details about its uses, see this article.
* Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Femara can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days or weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.
These are just a few of the more common side effects reported by people who took Femara in clinical trials:
- high cholesterol
- hot flashes
- low bone density (low levels of calcium and minerals in your bones)*
- weight gain*
- joint pain*
* To learn more about this side effect, see the “Side effect specifics” section below.
Mild side effects can occur with Femara use. This list doesn’t include all the possible mild side effects of the drug. For more information, you can refer to Femara’s prescribing information.
Mild side effects that have been reported with Femara include:
- dizziness
- edema (swelling that usually affects your hands, feet, legs, or arms)
- excessive sweating
- feeling drowsy, weak, or tired
- fatigue (lack of energy)
- flushing (temporary warmth, redness, or deepening of skin color)
- hot flashes
- muscle pain or bone pain
- nausea
- vaginal bleeding or spotting
- weight changes, such as weight gain or loss*
- hair loss*
- joint pain*
- headache*
These side effects may be temporary, lasting a few days or weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.
Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Femara and want to tell the FDA about it, visit MedWatch.
* To learn more about this side effect, see the “Side effect specifics” section below.
Femara may cause serious side effects. These were common in clinical studies of the drug. The list below may not include all the possible serious side effects of the drug. For more information, you can refer to Femara’s prescribing information.
If you develop serious side effects while taking Femara, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.
Serious side effects that have been reported include:
- high cholesterol, which doesn’t usually cause any symptoms
- low bone density (low levels of calcium and minerals in your bones)*
- allergic reaction*†
* To learn more about this side effect, see the “Side effect specifics” section below.
† An allergic reaction is possible after taking Femara. But this side effect wasn’t reported in clinical studies.
Femara may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.
Can Femara be used to treat infertility? If so, what are its side effects when used for this purpose?
Femara isn’t approved by the Food and Drug Administration (FDA) to treat infertility. But it’s sometimes prescribed off-label for this use. Off-label means using a drug for a purpose other than what it’s approved for.
In females,* infertility is the inability to become pregnant or stay pregnant. To learn how Femara treats infertility, see this article.
When used for infertility, side effects of Femara are expected to be the same as when the drug is used to treat breast cancer.† But females* in clinical studies of Femara for infertility reported some additional side effects such as:
If you have questions about taking Femara for infertility, talk with your doctor.
* Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
† For more information, see “Mild side effects of Femara” and “Serious side effects of Femara” above.
Could I have side effects of Femara after stopping treatment?
No, it isn’t likely. Stopping treatment with Femara isn’t known to cause side effects or withdrawal symptoms. Withdrawal symptoms are side effects that can happen when you stop taking a drug your body has become used to.
It is possible, however, that you might continue to experience side effects of Femara for about a week after your last dose. This is because the drug can stay in your system for about 7 days after you stop the treatment.
Even though stopping Femara isn’t known to cause side effects, you shouldn’t stop taking the drug unless your doctor says it’s safe to do so. If you have questions about what to expect after stopping Femara treatment, talk with your doctor.
Does Femara cause long-term side effects? If so, how long do the side effects last?
Most side effects of Femara are short term. In many cases, the side effects should go away either shortly after your body gets used to Femara or soon after you stop taking the drug. But some side effects of Femara might last longer.
Examples of side effects that may be long term include low bone density (low levels of calcium and minerals in your bones). This can lead to:
- osteoporosis (brittle, weak bones)
- bone fractures (broken bones)
If you’re concerned about any long-term side effects from taking Femara, talk with your doctor.
What could be the side effects of a Femara 7.5-mg dose?
The usual dosage of Femara for treating breast cancer is 2.5 milligrams (mg) once per day. But your doctor might prescribe a higher dosage for you if needed. And higher dosages of the drug can increase your risk for side effects from Femara.
For examples of side effects that may happen after taking 7.5 mg of Femara, see “Mild side effects of Femara” and “Serious side effects of Femara” above.
What are the side effects of Femara vs. Clomid?
Clomid was a brand-name prescription drug that’s no longer available. But the generic version of Clomid (called clomiphene) is currently available. A generic drug is an exact copy of the active ingredient in a brand-name drug.
Femara and clomiphene can cause similar side effects. But the drugs can cause some different side effects, as well. In the table below are examples of common side effects that can occur with Femara, with clomiphene, or with both drugs when they’re taken individually:
| Can occur with Femara | Can occur with clomiphene | Can occur with both Femara and clomiphene |
| • high cholesterol • low bone density (low levels of calcium and minerals in your bones) • joint pain | • enlarged ovaries • eye problems, such as blurry vision | • weight gain • abdominal (belly) bloating • breast pain • hot flashes • vaginal bleeding or spotting |
Both Femara and clomiphene may be prescribed to treat infertility in females.* Femara isn’t approved by the FDA for this use. But it’s sometimes prescribed off-label† to treat infertility. Clomiphene is FDA-approved to treat infertility.
To learn more about how Femara compares with clomiphene, see this article. And for more information about side effects that Femara may cause, see “Mild side effects of Femara” and “Serious side effects of Femara” above. If you have more questions about how the side effects of Femara and clomiphene compare, talk with your doctor.
* Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
† Off-label means using a drug for a purpose other than what it’s approved for.
Learn more about some of the side effects that Femara may cause.
Weight changes, such as weight gain or loss
Weight changes were a common side effect in clinical studies of Femara. Both weight gain and weight loss were reported in studies of the drug, although weight gain was more common.
Keep in mind that cancer (including breast cancer, which Femara is used to treat) can often cause changes in body weight.
What you can do
If you’re concerned about weight changes while taking Femara, talk with your doctor. They can suggest healthy ways to manage your weight.
Hair loss
Hair loss is a possible side effect of Femara. In clinical studies, this side effect was common.
What you can do
Talk with your doctor about ways to manage any hair loss you experience while taking Femara. Your doctor may suggest that you use a cooling cap to help with hair loss. Cooling caps are devices that decrease blood flow to your scalp. This can lower the amount of Femara that reaches your hair follicles, which can help reduce hair loss from the drug.
Joint pain
Joint pain was a common side effect reported in clinical studies of Femara. It isn’t known how long this side effect might last after stopping Femara treatment.
What you can do
Tell your doctor about any joint pain that’s bothersome or doesn’t go away within a few days.
To relieve your joint pain, consider asking your doctor about taking over-the-counter pain relievers. Examples include ibuprofen (Advil, Motrin) and acetaminophen (Tylenol). But be sure to talk with your doctor or pharmacist before taking any new medications with Femara.
Your doctor may also check for other causes of joint pain, such as bone fractures (broken bones). For more information about your risk for fractures with Femara, see “Low bone density” just below.
Headache
Headache was a common side effect in clinical studies of Femara. How long headaches might continue to occur after you stop taking Femara isn’t known.
What you can do
If you have headaches that don’t go away quickly, you could ask your doctor about trying over-the-counter pain relievers, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). But before taking any new medications with Femara, talk with your doctor or pharmacist to make sure it’s safe.
If your headaches don’t stop happening within a few days or if they bother you, talk with your doctor. They may suggest other ways to relieve this side effect.
Low bone density
Taking Femara can cause low bone density (low levels of calcium and minerals in your bones). Bone density may also be referred to as bone mineral density. Decreased bone density can lead to osteoporosis (brittle, weak bones) and bone fractures (broken bones).
Low bone density was a common side effect in clinical studies of Femara.
What you can do
While you’re taking Femara, your doctor may check your bone density. This helps them monitor the strength of your bones. If your bone density gets low during treatment, your doctor may prescribe a drug to help strengthen your bones.
If you’re concerned about Femara’s potential effects on your bone density, talk with your doctor.
Allergic reaction
As with most drugs, Femara can cause an allergic reaction in some people. But this side effect wasn’t reported in clinical studies.
Symptoms can be mild or serious and can include:
- rash
- itching
- flushing (temporary warmth, redness, or deepening of skin color)
- swelling under your skin, typically in your lips, eyelids, feet, or hands
- swelling of your mouth, tongue, or throat, which can make it hard to breathe
What you can do
For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Femara. But if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.
Be sure to talk with your doctor about your health history before you take Femara. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:
High cholesterol. Femara may cause high cholesterol levels. Due to the risk of this side effect, your doctor will likely recommend cholesterol tests while you’re taking the drug. If your cholesterol levels become too high, your doctor may prescribe cholesterol-lowering drugs.
Osteoporosis. Before starting Femara, tell your doctor if you have osteoporosis (brittle, weak bones). Taking Femara can cause low bone density (low levels of calcium and minerals in your bones). And this can cause osteoporosis to develop or get worse. Low bone density can also lead to bone fractures (broken bones). You may have an increased risk for low bone density if you already have osteoporosis before starting Femara.
If you have osteoporosis, your doctor may prescribe medication to help protect your bones during Femara treatment. They will likely monitor your bone mineral density during the treatment, as well.
Severe liver problems. Your liver helps clear Femara from your body. If you have severe liver problems, such as cirrhosis (scarring of the liver), your doctor may prescribe a dosage of Femara that’s lower than usual. Be sure to tell your doctor if you have severe liver problems before starting Femara.
Allergic reaction. You shouldn’t take Femara if you’ve ever had an allergic reaction to the drug or any of its ingredients. Talk with your doctor about which other treatments are better choices for you.
Pregnancy. You shouldn’t take Femara during pregnancy. For more information, see the “Pregnancy and breastfeeding while taking Femara” section below.
Breastfeeding. You shouldn’t breastfeed or become pregnant for at least 3 weeks after your last dose of Femara. For more information, see “Pregnancy and breastfeeding while taking Femara” below.
Alcohol use with Femara
There aren’t any known interactions between Femara and alcohol.
However, alcohol can cause side effects that are similar to those of Femara. So drinking alcohol while taking Femara could worsen certain side effects of the drug.
Examples of these side effects include:
- dizziness
- feeling drowsy, weak, or tired
- fatigue (lack of energy)
- flushing (temporary warmth, redness, or deepening of skin color)
- hot flashes
- nausea
If you drink alcohol, talk with your doctor about the amount that’s safe for you to drink while taking Femara.
Pregnancy and breastfeeding while taking Femara
You shouldn’t take Femara while pregnant or breastfeeding. You also shouldn’t breastfeed or become pregnant for at least 3 weeks after your last dose of the drug. This is because the drug can stay in your system for up to a few weeks after your last dose.
If you’re pregnant or planning a pregnancy, talk with your doctor. You should also tell your doctor if you’re breastfeeding or planning to breastfeed. Your doctor can recommend treatment options other than Femara.
Mild and serious side effects can occur while you take Femara. Most side effects are mild and will go away within a few hours or days after you start taking the drug. But be sure to tell your doctor if you have bothersome side effects that last for more than a few days.
If you’d like to learn more about Femara, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.
Besides talking with your doctor, you can do some research on your own. These articles might help:
- More information about Femara. For details about other aspects of Femara, refer to this article.
- A look at breast cancer. For details about breast cancer, see our cancer hub, as well as our list of breast cancer articles.
Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.