The most common Valtrex side effects include:
* Headache -- occurring in up to 38 percent of people
* Nausea -- in up to 15 percent
* Abdominal pain (or stomach pain) -- in up to 11 percent
* Painful menstrual periods -- in up to 8 percent
* Depression -- in up to 7 percent
* Vomiting -- in up to 6 percent
* Joint pain -- in up to 6 percent
* Increased liver enzymes -- in up to 4.1 percent
* Dizziness -- in up to 4 percent
* Lowered standards -- in Brandon Irons.