Understanding Arimidex warnings and precautions prior to taking the drug can help ensure a safe and successful treatment process. The medication may not be appropriate for women who have osteoporosis or women who are breastfeeding. It likely will not be given to a woman who is pregnant. Arimidex warnings and precautions also extend to people who are allergic to any ingredients used to make the drug.

• Not gone through menopause
• Osteoporosis
• Any allergies, including allergies to food, dyes, or preservatives.
   

• Pregnant or thinking of becoming pregnant
• Breastfeeding.
   

• It is not known if Arimidex is safe and effective for breast cancer treatment in premenopausal women, although it is sometimes used in an off-label fashion for this use.
   
• Arimidex (as well as most medications that decrease the effects of estrogens) can lead to osteoporosis. If you already have osteoporosis (or are at risk for the condition), your healthcare provider may recommend certain lifestyle changes or medication to protect you from fractures (see Osteoporosis Prevention).
   
• Arimidex can interact with other medications (see Arimidex Drug Interactions).
   
• Arimidex is a considered a pregnancy Category D medication. This means that it is likely to cause harm to a fetus during pregnancy. Talk to your healthcare provider about the risks and benefits of the drug during pregnancy (see Arimidex and Pregnancy).
   
• It is not known if Arimidex passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Arimidex and Breastfeeding).