See also Warning section.

Before taking hydroxyurea, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: other blood/bone marrow problems (such as low red/white blood cells and platelets), kidney disease, liver disease, HIV infection, high uric acid level in the blood, radiation treatment.

Hydroxyurea can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Tell your health care professional that you are using hydroxyurea before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug.

It is unknown if this medication affects sperm. If you plan to father a child, discuss the risks and benefits of this medication with your doctor.

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using hydroxyurea. Hydroxyurea may harm an unborn baby. Women using this medication should ask about reliable forms of birth control during treatment and for 6 months after the last dose. Men using this medication should ask about reliable forms of birth control during treatment and for 1 year after the last dose. If you or your partner becomes pregnant, talk to your doctor right away about the risks and benefits of this medication.

Hydroxyurea passes into breast milk and may have undesirable effects on a nursing infant. Breastfeeding is not recommended while using this medication. Consult your doctor before breastfeeding.