Hepatitis B virus reactivation: Before starting HARVONI treatment, your healthcare provider will do blood tests to check for hepatitis B infection. If you have ever had hepatitis B, the hepatitis B virus could become active again during and after treatment with HARVONI. This may cause serious liver problems, including liver failure and death. If you are at risk, your healthcare provider will monitor you during and after taking HARVONI.

Tell your healthcare provider about all of your medical conditions, including if you have ever had hepatitis B infection, liver problems other than hepatitis C infection, or a liver transplant; if you have severe kidney problems or are on dialysis; if you have HIV; or if you are pregnant or breastfeeding or plan to become pregnant or breastfeed. It is not known if HARVONI will harm your unborn baby or pass into your breast milk. If you take HARVONI with ribavirin, you should also read the ribavirin Medication Guide for important pregnancy-related information.

Tell your healthcare provider and pharmacist about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. HARVONI and certain other medicines may affect each other, or may cause side effects.

Slow heart rate (bradycardia): HARVONI, when taken with amiodarone (Cordarone®, Nexterone®, Pacerone®), a medicine used to treat certain heart problems, may cause slow heart rate, which in some cases has led to death or the need for a pacemaker. Get medical help right away if you take amiodarone with HARVONI and get any of the following symptoms: fainting or near-fainting, dizziness or lightheadedness, not feeling well, weakness, extreme tiredness, shortness of breath, chest pains, confusion, or memory problems.
The most common side effects of HARVONI include tiredness, headache, and weakness.