Get emergency medical help if you have signs of an allergic reaction to valacyclovir: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
confusion, aggression, or you feel shaky or unsteady;
hallucinations (seeing or hearing things that are not real);
problems with speech;
a seizure (convulsions); or
kidney problems--little or no urination, painful or difficult urination, swelling in your feet or ankles, feeling tired or short of breath.
Stop taking valacyclovir and call your doctor right away if you have any of the following signs of a serious side effect that can harm red blood cells:
fever, pale skin;
unusual bleeding (nosebleeds, bleeding gums);
red or pink urine, little or no urination;
red spots on the skin (not related to herpes or chickenpox);
feeling weak or tired;
stomach pain, bloody diarrhea, vomiting; or
swelling in your face, hands, or feet.
Side effects may be more likely in adults who are 65 or older.
Common valacyclovir side effects may include:
nausea, stomach pain; or
headache.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Valacyclovir side effects (more detail)
