Before you begin taking a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take Letrozole.

Blood Clots: Letrozole may cause an increase in the formation of blood clots in blood vessels, reducing the blood flow to organs or the extremities. In the arms or legs this is experienced as pain, swelling, warmth, or redness in the limb. In the lungs, you may experience difficulty breathing, sharp chest pain, coughing, or coughing up blood. If you experience any of these symptoms, contact your doctor immediately.

Bone mineral density: Long-term use of letrozole may decrease the density of bones, thereby increasing the risk of Osteoporosis. Your doctor will order bone mineral density tests periodically while you are taking letrozole.

Cholesterol: Letrozole may increase cholesterol levels. If you have increased blood cholesterol levels or a history of increased cholesterol, discuss with your doctor how Letrozole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Letrozole, and whether any special monitoring is needed.

Drowsiness/dizziness: Letrozole may cause dizziness or drowsiness. If you experience either or both of these side effects, you should not drive, use machinery, or perform any other activities that require alertness.

Heart disease: Letrozole may increase the risk of heart attack or increased blood pressure. If you are at risk for heart disease or high blood pressure, discuss with your doctor how Letrozole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Letrozole, and whether any special monitoring is needed. If you experience signs of a heart attack, such as tightness or heaviness in your chest, sudden chest pain spreading to your arms or shoulders, sweating, nausea, or anxiety, seek medical help immediately.

Kidney function: If you have reduced kidney function, discuss with your doctor how Letrozole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Letrozole, and whether any special monitoring is needed.

Liver function: If you have liver disease or reduced liver function, discuss with your doctor how Letrozole may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Letrozole, and whether any special monitoring is needed.

Premenopausal women: Letrozole should not be taken by women who have not reached menopause (either naturally or surgically), unless the potential benefits outweigh the risks.

Stroke: Letrozole increases the risk of a stroke or "mini-strokes" occurring as a result of blood clots forming in the blood vessels. If you experience signs of a stroke or mini-stroke, such as confusion, difficulty speaking, loss of coordination, sudden headache or vision changes, contact your doctor immediately.

Pregnancy: It is suspected that the use of letrozole during pregnancy could cause miscarriages and other serious problems. It is not intended to be taken by women who have not reached menopause.

Letrozole should not be taken during pregnancy unless the benefits outweigh the risks. Any woman taking Letrozole who may become pregnant should practice effective birth control and contact her doctor immediately if pregnancy is suspected while taking Letrozole.

Breast-feeding: It is not known if letrozole passes into breast milk. If you are a breast-feeding mother and are taking Letrozole, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of Letrozole have not been established for children. Children under 18 years of age should not use Letrozole.