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Valacyclovir

Brand names: Valtrex

Valacyclovir treats outbreaks of shingles, cold sores, and genital herpes, and can prevent herpes outbreaks.

Brand namesValtrex
Type of medicineAntiviral
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It doesn't cure herpes viruses but shortens outbreaks and lowers spread. It works best when started early.

What it's used for

  • Shingles
  • Cold sores
  • Genital herpes (outbreaks and daily prevention)

How to take it

  • Start at the first tingle or sign of an outbreak.
  • Take it with or without food. Drink plenty of fluids.
  • Daily suppression lowers the chance of passing genital herpes to a partner; condoms add protection.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Headache
  • Nausea
  • Stomach pain
Call your provider todayConfusion, agitation, or seeing things (more likely in older adults or with kidney disease)
Call your provider todayPeeing much less
Call 911Fever, unusual bruising, and confusion (rare blood disorder)

Warnings

  • Doses are lower with kidney disease.
  • Shingles near the eye needs same-day care.

Other medicines, foods, and alcohol

  • Other medicines that affect the kidneys may need monitoring.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Commonly used in pregnancy when needed.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember. If it's almost time for the next dose, skip the missed one. Don't double up, and still finish the full course.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.