How long you take valacyclovir depends on what you’re treating. For cold sores, it can be as short as a single day. For recurrent genital herpes, the typical course is 3 to 5 days. For shingles, it’s 7 to 10 days. And for daily suppressive therapy to prevent outbreaks, some people stay on it for months or years. Here’s a breakdown by condition so you can understand what to expect from your specific prescription.
Cold Sores: One Day
Cold sore treatment with valacyclovir is the shortest course available. The standard approach is two doses in a single day, spaced 12 hours apart. That’s it. This works best when you start at the first sign of a cold sore, ideally during the tingling or burning stage before a blister fully forms. If you wait until the sore is already well established, the medication is less effective at shortening the outbreak.
Recurrent Genital Herpes: 3 to 5 Days
If you get recurring genital herpes outbreaks and treat them individually (sometimes called episodic therapy), the course lasts 3 to 5 days depending on the regimen your provider prescribes. One common option is a 3-day course taken twice daily. Another is a 5-day course taken once daily. Both are considered effective.
Timing matters more here than many people realize. Treatment should begin within 24 hours of your first symptoms, whether that’s tingling, itching, burning, or the appearance of sores. Starting after that 24-hour window significantly reduces how well the medication works. Many people who get frequent outbreaks keep a prescription on hand so they can start immediately when they feel prodrome symptoms coming on.
First Genital Herpes Outbreak: 7 to 10 Days
A first episode of genital herpes is usually more severe and longer-lasting than recurrences. Because of this, the treatment course is longer, typically 7 to 10 days. Your provider may extend it further if sores haven’t fully healed by the end of that window. First outbreaks can take two to four weeks to resolve on their own, so starting antiviral treatment early can meaningfully shorten that timeline and reduce pain.
Shingles: 7 to 10 Days
For shingles (caused by the same virus family but a different strain than cold sores or genital herpes), the standard valacyclovir course runs 7 to 10 days. Ideally, you should start the medication within 72 hours of your first symptoms. The sooner you begin, the better your chances of reducing the severity of the rash and lowering your risk of lingering nerve pain, which can persist for weeks or months after the rash clears.
If shingles affects the eye area, the 7 to 10 day course is especially important. This form carries a higher risk of complications, and completing the full course helps protect your vision.
Daily Suppressive Therapy: Months to Years
Some people with frequent genital herpes outbreaks (generally six or more per year) take valacyclovir every day to prevent flare-ups rather than treating them one at a time. This is called suppressive therapy, and it’s the one situation where you may take valacyclovir continuously for a long stretch.
Daily suppressive therapy reduces outbreak frequency by roughly 70 to 80 percent for most people. It also lowers the risk of transmitting herpes to a sexual partner. There’s no hard rule on how long to continue. Many people stay on it for a year or more, then reassess with their provider whether to keep going. Outbreaks often become less frequent over time, so some people eventually stop daily therapy and switch to episodic treatment as needed.
Long-term use of valacyclovir for suppression has been studied over several years and is generally well tolerated. The most common side effects are headache and nausea, and these tend to be mild. People with kidney problems may need dose adjustments, since the drug is processed through the kidneys.
Why Finishing the Full Course Matters
Unlike antibiotics, valacyclovir doesn’t kill the virus. It works by blocking the virus from copying itself, which limits how much damage it can do during an active outbreak. Stopping early won’t create drug resistance the way skipping antibiotics might, but it can mean your outbreak lasts longer or your symptoms don’t fully resolve. Completing the prescribed number of days gives the medication its best chance of working.
If you miss a dose, take it as soon as you remember. If it’s almost time for your next dose, skip the missed one and continue on schedule. Don’t double up to make up for it.
Starting Early Makes the Biggest Difference
Across every condition valacyclovir treats, the single biggest factor in how well it works is how quickly you start. Within 24 hours is the target for cold sores and genital herpes outbreaks. Within 72 hours is the goal for shingles. After those windows, the virus has already replicated enough that the medication has less to work with. If you know your body’s early warning signs, keeping valacyclovir accessible so you can begin at the first hint of symptoms will get you the most benefit from the shortest course.