Aciclovir 800 Tablet is an antiviral medicine. It helps in treating viral infections like herpes labialis, herpes simplex, shingles, genital herpes infection, and chickenpox. It prevents the multiplication of virus in human cells and therefore helps in clearing the infection. Aciclovir 800 Tablet should be taken in the dose and duration as advised by your doctor. Do not skip any doses and finish the full course of treatment even if you feel better. Dissolve it in a glass of water before taking it. It may be taken with or without food, but it is better to take it at a fixed time. If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular schedule. Do not double the dose. You should drink plenty of water while on treatment with this medicine as it helps to prevent dehydration and kidney damage. Some side effects of this medicine include headache, dizziness, vomiting, nausea, fatigue, and fever. Inform your doctor if these side effects do not resolve or persist for a longer duration. Please consult your doctor if you are pregnant, planning to conceive or breastfeeding.