Letrozole Side Effects
Medically reviewed by Drugs.com. Last updated on Jan 14, 2021.
Commonly reported side effects of letrozole 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 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:
- Bone fracture
- breast pain
- chest pain
- chills, fever, or flu-like symptoms
- mental depression
- swelling of the feet or lower legs
- Continuing or severe nervousness
- dizziness or lightheadedness
- fast heartbeat
- heart attack
- increased sweating
- pain in the chest, groin, or legs, especially the calves
- severe and sudden, unexplained troubled breathing
- severe, sudden headache
- slurred speech
- sudden loss of coordination
- sudden, severe weakness or numbness in the arm or leg
- swollen glands
- vaginal bleeding
- vision changes
Incidence not known
- Black, tarry stools
- 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:
- dry mouth
- increased thirst
- loss of appetite or weight loss
- metallic taste
- skin rash or itching
- spinning or whirling sensation causing loss of balance
- stomach pain or upset
- trouble sleeping
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
- 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%)
Very common (10% or more): Nausea (17%), constipation (11%)
Common (1% to 10%): Vomiting, diarrhea, abdominal pain, dyspepsia
Common (1% to 10%): Influenza, peripheral edema, pain, post-mastectomy lymphedema, thromboembolic event, viral infection
Uncommon (0.1% to 1%): Pyrexia, mucosal dryness, thirst
Common (1% to 10%): Myalgia, bone pain, osteopenia, decreased lumbar spine bone mineral density
Postmarketing reports: Trigger finger[Ref]
Very common (10% or more): Headache (20%), dizziness/lightheadedness (14%)
Uncommon (0.1% to 1%): Memory impairment, dysesthesia (hypesthesia/paresthesia), taste and thirst disturbance, carpal tunnel syndrome
Rare (less than 0.1%): Cerebrovascular infarction
Very common (10% or more): Dyspnea (18%), cough (13%)
Common (1% to 10%): Chest wall pain
Very common (10% or more): Increased sweating (24%)
Uncommon (0.1% to 1%): Urticaria
Uncommon (0.1% to 1%): Increased hepatic enzymes
Very rare (less than 0.01%): Hepatitis[Ref]
Uncommon (0.1% to 1%): Leukopenia
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
Very common (10% or more): Vaginal bleeding (13%)
Common (1% to 10%): Vaginal irritation, vaginal hemorrhage, vulvovaginal dryness, breast pain, urinary tract infection
Very rare (less than 0.01%): Anaphylactic reactions[Ref]
Common (1% to 10%): Secondary malignancy
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
- How many cycles of letrozole are needed to get pregnant?
- How does Femara affect your period?
- What happens when you stop taking letrozole?
- How long do letrozole side effects last?
- When do you ovulate on Femara (letrozole)?
- When will I ovulate after taking letrozole?
- Does Femara make your hair fall out?
- Can Femara cause twins?
- Does letrozole affect blood sugar levels?
- Is letrozole a form of chemotherapy?
- What is the success rate for Femara in breast cancer?
- Aromasin vs Femara - how do they compare?
- Which is better - Aromasin or Femara?
- How do you take letrozole for fertility?
- What is Femara (letrozole) and what is it used for?
More about letrozole
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- Compare Alternatives
- Support Group
- Pricing & Coupons
- En Español
- 283 Reviews
- Drug class: aromatase inhibitors
- Other brands
Related treatment guides
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
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.