Before taking potassium iodide, tell your doctor or pharmacist if you are allergic to it; or to iodine; 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: current attack/worsening of bronchitis (if taking potassium iodide to thin mucus in the lungs), a certain type of skin condition (dermatitis herpetiformis), a certain type of blood vessel disease (hypocomplementemic vasculitis), certain thyroid disorders (such as multinodular goiter, Graves' disease, autoimmune thyroiditis, nodular thyroid disease with heart disease), overactive thyroid disease (unless you are specifically prescribed potassium iodide to treat hyperthyroidism), tuberculosis, high potassium blood level, kidney disease, Addison's disease, a certain muscle disorder (myotonia congenita).

Caution is advised when this drug is given to newborn babies younger than 1 month old. Treatment for more than 1 day should be avoided because repeated dosing increases the risk of blocking thyroid function, possibly affecting the newborn's brain development. If treatment is needed for longer than 1 day, discuss the risks and benefits with the doctor. Treated babies should be given thyroid function tests.

During pregnancy, this medication should be used only when clearly needed. Treatment for more than 1 day should be avoided because repeated dosing increases the risk of blocking thyroid function in the unborn baby, possibly causing harm. If treatment is needed for longer than 1 day, discuss the risks and benefits with your doctor.

Caution is advised when this drug is used by women who are breastfeeding. This drug passes into breast milk. Treatment for more than 1 day should be avoided if you are breastfeeding because repeated dosing increases the risk of blocking thyroid function in the nursing infant. This effect may cause harm, especially in newborns younger than 1 month old. If treatment is needed for longer than 1 day, discuss with your doctor the risks and benefits, as well as whether you should stop breastfeeding.