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Femara Side Effects

Generic name: letrozole

Medically reviewed by Last updated on Mar 30, 2022.

Note: This document contains side effect information about letrozole. Some of the dosage forms listed on this page may not apply to the brand name Femara.

In Summary

Common side effects of Femara include: bone fracture, arthralgia, edema, dizziness, fatigue, hypercholesterolemia, osteoporosis, and flushing. Other side effects include: myalgia. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to letrozole: oral tablet

Side effects requiring immediate medical attention

Along with its needed effects, letrozole (the active ingredient contained in Femara) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking letrozole:

Less common

  • Bone fracture
  • breast pain
  • chest pain
  • chills, fever, or flu-like symptoms
  • mental depression
  • swelling of the feet or lower legs


Incidence not known

  • Black, tarry stools
  • blindness
  • blurred vision
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • chest discomfort
  • dark urine
  • decreased vision
  • dilated neck veins
  • extreme tiredness or weakness
  • general tiredness or weakness
  • increased need to urinate
  • irregular breathing
  • irregular heartbeat
  • light-colored stools
  • painful or difficult urination
  • passing urine more often
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • upper right abdominal pain
  • weight gain
  • white or brownish vaginal discharge
  • yellow eyes and skin

Side effects not requiring immediate medical attention

Some side effects of letrozole may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

Incidence not known

  • Bad, unusual, or unpleasant (after) taste and thirst
  • being forgetful
  • change in taste
  • dryness of the skin
  • hair loss
  • hives or welts
  • increased appetite
  • irritability
  • nervousness
  • red, sore eyes
  • redness of the skin
  • swelling or inflammation of the mouth

For Healthcare Professionals

Applies to letrozole: oral tablet


Very common (10% or more): Hot flash/flushing (50%), cardiovascular disease (14%), other cardiovascular event (13%)

Common (1% to 10%): Hypertension, chest pain, cardiac event (angina, coronary heart disease, myocardial ischemia, myocardial infarction), cardiac failure

Uncommon (0.1% to 1%): Palpitation, tachycardia, arterial thrombosis[Ref]


Very common (10% or more): Nausea (17%), constipation (11%)

Common (1% to 10%): Vomiting, diarrhea, abdominal pain, dyspepsia

Uncommon (0.1% to 1%): Stomatitis, dry mouth[Ref]


Very common (10% or more): Fatigue/lethargy/malaise/asthenia (34%), edema (18%), night sweats (15%)

Common (1% to 10%): Influenza, peripheral edema, pain, post-mastectomy lymphedema, thromboembolic event, viral infection

Uncommon (0.1% to 1%): Pyrexia, mucosal dryness, thirst

Frequency not reported: Peripheral thromboembolic event (venous thrombosis, thrombophlebitis, portal vein thrombosis, pulmonary embolism)[Ref]


Very common (10% or more): Arthralgia/arthritis (25%), bone fracture (22%), musculoskeletal pain/back pain/arm pain/leg pain (22%), osteoporosis (15%), extremity/limb pain (10%)

Common (1% to 10%): Myalgia, bone pain, osteopenia, decreased lumbar spine bone mineral density

Postmarketing reports: Trigger finger[Ref]

Nervous system

Very common (10% or more): Headache (20%), dizziness/lightheadedness (14%)

Common (1% to 10%): Somnolence, cerebrovascular events (transient ischemic attack, thrombotic or hemorrhagic stroke, hemiparesis development)

Uncommon (0.1% to 1%): Memory impairment, dysesthesia (hypesthesia/paresthesia), taste and thirst disturbance, carpal tunnel syndrome

Rare (less than 0.1%): Cerebrovascular infarction

Frequency not reported: Vertigo[Ref]


Very common (10% or more): Dyspnea (18%), cough (13%)

Common (1% to 10%): Chest wall pain

Frequency not reported: Pleural effusion[Ref]


Very common (10% or more): Increased sweating (24%)

Common (1% to 10%): Alopecia, dry skin, rash (erythematous, maculopapular, psoriasiform, vesicular), pruritus

Uncommon (0.1% to 1%): Urticaria

Very rare (less than 0.01%): Angioedema, toxic epidermal necrolysis, erythema multiforme[Ref]


Uncommon (0.1% to 1%): Increased hepatic enzymes

Very rare (less than 0.01%): Hepatitis[Ref]


Uncommon (0.1% to 1%): Leukopenia

Frequency not reported: Decreased lymphocyte count, thrombocytopenia[Ref]


Common (1% to 10%): Cataract

Uncommon (0.1% to 1%): Eye irritation, blurred vision[Ref]


Very common (10% or more): Hypercholesterolemia (53%), increased weight (13%)

Common (1% to 10%): Decreased weight, anorexia, increased appetite

Frequency not reported: Hypercalcemia[Ref]


Very common (10% or more): Vaginal bleeding (13%)

Common (1% to 10%): Vaginal irritation, vaginal hemorrhage, vulvovaginal dryness, breast pain, urinary tract infection

Uncommon (0.1% to 1%): Increased urinary frequency, vaginal discharge[Ref]


Very rare (less than 0.01%): Anaphylactic reactions[Ref]


Common (1% to 10%): Secondary malignancy

Uncommon (0.1% to 1%): Endometrial hyperplasia/cancer, endometrial proliferation disorder, tumor pain

Rare (less than 0.1%): Other endometrial disorder

Frequency not reported: Stomatitis cancer pain[Ref]


Common (1% to 10%): Depression, insomnia

Uncommon (0.1% to 1%): Anxiety, nervousness, irritability[Ref]


Common (1% to 10%): Renal disorders[Ref]

Frequently asked questions


1. "Product Information. Femara (letrozole)." Novartis Pharmaceuticals, East Hanover, NJ.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. Cerner Multum, Inc. "Australian Product Information." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.