Higher doses, more frequent doses, longer therapy, and combination therapies are being tested. The most common serious side effect is depression, particularly in patients with a prior history. Most patients will have muscle aches, fatigue and low grade fevers. Nausea and diarrhea are common as is irritation of the skin at the injection site. Patients may experience significant weight loss, and if this occurs the dose should be adjusted.
Patients often complain of irritability and headaches.
A small number of patients may develop thyroid disease. Normal thyroid function should be documented prior to treatment. Hair loss is not uncommon, but usually reversible. Few side effects are severe or persist after treatment. Interferon should not be given to women considering pregnancy, nor to the intended father.