Can Letrozole Cause Side Effects?

Letrozole, also known by its brand name Femara, is a medication used in the treatment of breast cancer. It belongs to a class of drugs called aromatase inhibitors, which work by blocking the production of estrogen in postmenopausal women. This helps to slow down or stop the growth of certain types of breast tumors that require estrogen to grow.

Letrozole is often prescribed as part of a treatment plan for hormone receptor-positive breast cancer and has been shown to be effective in reducing the risk of recurrence. However, like any medication, letrozole may cause side effects in some individuals. In this article, we will discuss the potential side effects of letrozole and how they can be managed.

Common Side Effects

Can Letrozole Cause Side Effects?

There are several common side effects associated with letrozole that affect a significant number of patients. These include:

Hot flashes

Hot flashes are one of the most commonly reported side effects of letrozole. They are sudden feelings of intense heat, often accompanied by flushing and sweating. Hot flashes can occur at any time but are more frequent in menopausal women due to hormonal changes. Letrozole works by reducing estrogen levels, which can trigger hot flashes as estrogen plays a role in regulating body temperature.

If you experience hot flashes while taking letrozole, try to avoid triggers such as spicy foods, caffeine, and alcohol. Dress in layers to easily remove clothing when necessary. Deep breathing exercises and relaxation techniques may also help to alleviate hot flashes.

Joint Pain

Another common side effect of letrozole is joint pain or stiffness. This can range from mild discomfort to severe pain and may affect different areas of the body, including hands, wrists, knees, and hips. Letrozole can cause joint pain by reducing estrogen levels, which play a role in maintaining bone density and lubricating joints.

If you experience joint pain while taking letrozole, talk to your doctor about possible treatments such as over-the-counter pain relievers or physical therapy exercises. Maintaining a healthy weight and staying physically active can also help to reduce joint pain.


Headaches are another common side effect of letrozole, affecting approximately one-third of patients. These headaches may be mild or severe and can occur at any time during treatment. They may be caused by changes in hormone levels or other factors, such as stress or dehydration.

If you experience headaches while taking letrozole, make sure to drink plenty of water and try to manage stress levels. Over-the-counter pain relievers may also help alleviate headaches, but consult with your doctor if they persist or become severe.


Fatigue, or extreme tiredness, is a common side effect reported by patients taking letrozole. This may be due to changes in hormone levels or the body adjusting to the medication. It can significantly impact daily activities and quality of life.

If you experience fatigue while taking letrozole, make sure to get enough rest and prioritize tasks. Gentle exercises like walking or yoga may also help to increase energy levels. If fatigue continues, talk to your doctor as it may be a sign of anemia or other underlying conditions.

Nausea and Vomiting

Nausea and vomiting are potential side effects of letrozole, though they are less common than others. These symptoms can occur due to changes in hormone levels or as a side effect of other medications taken alongside letrozole.

If you experience nausea and vomiting while taking letrozole, make sure to stay hydrated and eat small, frequent meals throughout the day instead of large ones. Ginger supplements or teas may also help to alleviate these symptoms.

Less Common Side Effects

While less common than the side effects mentioned above, letrozole may also cause other side effects in some individuals. These include:

  • Insomnia: Difficulty falling or staying asleep may occur while taking letrozole. Practice good sleep hygiene habits to improve sleep quality.
  • Mood changes: Letrozole can affect hormone levels, which can lead to mood swings or irritability. Talk to your doctor if these symptoms persist.
  • Hair loss: Some individuals may experience hair thinning or loss while taking letrozole. This is usually temporary and hair growth should return after treatment ends.
  • Risk of osteoporosis: Letrozole may increase the risk of bone loss and osteoporosis in postmenopausal women. Consult with your doctor about ways to maintain healthy bones, such as calcium and vitamin D supplements or exercise.
  • Vision changes: Rarely, letrozole may cause vision changes such as blurred vision or eye pain. If you experience these symptoms, seek medical attention immediately.

It is essential to discuss any side effects you experience with your doctor as they may be able to offer solutions or adjustments to your treatment plan. Remember that the benefits of letrozole in treating breast cancer often outweigh the potential side effects. With proper management, most individuals can successfully complete their treatment with letrozole and reduce their risk of recurrence.

Pros and Cons of Letrozole

Here are some pros and cons to consider when taking letrozole:


  • Effective in reducing the risk of recurrence in hormone receptor-positive breast cancer.
  • May reduce the size or slow down the growth of tumors.
  • Can be taken orally as a once-daily medication.
  • Generally well-tolerated by most patients.
  • May also be used in the treatment of other hormone-related cancers, such as prostate and endometrial cancer.


  • May cause side effects such as hot flashes, joint pain, headaches, fatigue, nausea and vomiting.
  • Can increase the risk of osteoporosis in postmenopausal women.
  • Not suitable for use during pregnancy or breastfeeding.

It is essential to weigh the potential benefits and risks of letrozole with your doctor when considering this medication as part of your treatment plan. They can help you make an informed decision based on your individual situation and medical history.

Can any of these side effects be prevented?

While it is not possible to completely prevent all side effects, there are some steps you can take to minimize their impact. These include:

  • Communicating openly and regularly with your doctor about any side effects you experience.
  • Following a healthy lifestyle by maintaining a balanced diet, staying physically active, and managing stress levels.
  • Avoiding triggers such as alcohol, tobacco, and certain medications that may worsen side effects.
  • Following the recommended treatment plan and taking letrozole at the same time every day.
  • Talking to your doctor about potential medication interactions if you are taking other medications alongside letrozole.
  • Getting regular check-ups and blood tests to monitor your health while taking letrozole.

Remember, every individual may experience different side effects with letrozole, and what works for one person may not work for another. It is essential to work closely with your doctor to find the right treatment plan and manage any side effects that may occur.

Should I continue taking letrozole if I experience side effects?

If you experience any side effects while taking letrozole, it is crucial to talk to your doctor before making any changes to your medication. They may be able to adjust the dosage or offer alternative treatments to help manage side effects.

In most cases, the benefits of continuing with letrozole outweigh the potential side effects, and stopping treatment may increase the risk of cancer recurrence. However, if side effects become severe or impact your daily life significantly, your doctor may consider adjusting your treatment plan.

Plus, keep in mind that side effects usually improve with time as the body adjusts to letrozole. If you have any concerns or questions about your treatment plan, do not hesitate to discuss them with your doctor. They are there to support and guide you throughout your breast cancer journey.

Mistakes to avoid while taking letrozole

To get the most out of your treatment with letrozole, it is essential to avoid these common mistakes:

  • Skipping doses: It is crucial to take letrozole at the same time every day as prescribed by your doctor. Skipping doses or taking them irregularly may reduce the effectiveness of the medication.
  • Stopping treatment prematurely: It can be tempting to stop taking letrozole if you experience side effects. However, it is essential to discuss any concerns with your doctor before making any changes to your medication.
  • Not following up with check-ups and tests: It is crucial to attend all follow-up appointments and get regular blood tests while taking letrozole. This allows your doctor to monitor the effectiveness of the treatment and catch any potential side effects early on.
  • Not communicating with your doctor: It is vital to keep your doctor informed about any side effects or concerns you may have while taking letrozole. They can help you manage side effects and adjust your treatment plan accordingly.


Are there any alternative treatments to letrozole?

Yes, there are other hormonal therapy medications available for the treatment of hormone receptor-positive breast cancer, such as tamoxifen and anastrozole. It is essential to discuss with your doctor which option is best for you.

Is letrozole safe for long-term use?

The safety and effectiveness of letrozole for long-term use have not been established. It is important to follow your doctor’s recommendations and attend regular check-ups while taking letrozole.

Can I take letrozole with other medications?

It is crucial to inform your doctor of any other medications you are taking, including over-the-counter drugs and supplements, as they may interact with letrozole. Your doctor can advise on any necessary adjustments to your treatment plan.

Can letrozole prevent breast cancer?

No, letrozole is not a preventive medication for breast cancer. It is used as a treatment for hormone receptor-positive breast cancer after surgery or in combination with other treatments.


Letrozole is an effective and commonly used medication in the treatment of hormone receptor-positive breast cancer. While it may cause some side effects, the benefits often outweigh the risks for most patients. It is crucial to take letrozole as prescribed and communicate openly with your doctor about any concerns or side effects.

With proper management and monitoring, letrozole can help reduce the size of tumors and slow down their growth, improving outcomes for those with breast cancer.  So, it is essential to stay informed and work closely with your healthcare team throughout your treatment journey. Remember, you are not alone, and together, we can fight breast cancer.