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Valacyclovir (Valtrex) for Cold Sores: Common Treatment Questions Answered

Learn more about Valacyclovir (Valtrex) for cold sores including how it works, how to take it, and how effective it is.

Read on

With about 90% of adults over 50 testing positive for the HSV-1 virus, cold sores are a thing that many people have to deal with at least once in their lives.

20-40% of adults report having had at least one cold sore outbreak.

However, there may be an answer to shorten the duration of a cold sore...if you act fast.

Also Read: The 8 Cold Sore Stages (and What To Expect While Yours Is Healing)

What is Valacyclovir?

Valacyclovir is an antiviral medication that may help reduce the amount of time a cold sore will last.

Valacyclovir is considered a “prodrug” and it converts into acyclovir in the body.

But, by giving this medication in the Valacyclovir form vs Acyclovir, the bioavailability is increased about 3-5 fold.

Valacyclovir can help clear both the HSV-1 (cold sores) and HSV-2 (genital herpes) types of infections, but the dosing is different depending on what you are treating.

Valacyclovir also has indications for shingles and chickenpox, which are also forms of the herpes virus.


What does Valtrex do for cold sores?

Valacyclovir becomes Acyclovir which is a DNA polymerase inhibitor.

That means that Valacyclovir blocks the viral cell from making more DNA, meaning that the virus can’t properly replicate itself.

This then leads to less healthy cells infected with the HSV virus and a quicker time to clear.


How to take Valtrex for cold sores?

The best way to take Valacyclovir for cold sores is to be sure you have some on hand at the first sign of a cold sore.

Most people experience an initial tingling, itching, or burning sensation from a forming cold sore.

Once you notice these symptoms it is time to immediately start the following dosage:

  • Age >12: Take 2,000mg (2gm) every 12 hours for one day. (2 doses only)
  • Age <12: Usage and dose must be determined by your doctor.

Try to take the 2 doses as close to 12 hours apart as possible for the best results.

Do not take for more than 1 day for cold sore treatment.

During the treatment day, be sure to drink lots of water as Valacyclovir can be tough on your kidneys.

Remember, always take medications as directed by your doctor.


Learn More: Are Cold Sores Contagious?: How To Protect Yourself and Others

How fast does Valtrex work for cold sores?

The effects of reducing viral replication should begin as soon as the medication in your system, so the sooner you can take the medication once you feel a cold sore coming on, the better off you will be.

One study found that Valacyclovir may help shorten the duration of a cold sore outbreak by about 1 day.

And, since cold sores generally start healing on their own in 4-6 days time, you will be looking at something closer to 3-5 days.


How effective is Valtrex for cold sores?

In the same study that identified the 1 day overall shortened cold sore duration, they also found that about 8% of participants had completely blocked or prevented cold sores from Acyclovir treatment.

In this study the average time between initial symptoms and starting the first dose was about 6 hours, so timing is key!


Where can you find Valacyclovir?

Valacyclovir is a prescription-only medication, and cannot be found over the counter.

You can schedule an appointment with your local doctor or have an online questionnaire-based consultation with one of our Strut Health U.S. licensed doctors to see if Valacyclovir treatment is appropriate for you.

If you are a good candidate, your prescription can be shipped quickly and discreetly to your front door.



Over 90% of adults over 50 test positive for HSV-1, the virus responsible for annoying cold sores.

Valacyclovir is an oral antiviral medication that helps stop the replication of the virus.

For cold sore outbreaks for those 12 or older, the dosage is 2,000mg (2gm) every 12 hours for 1 day - so two doses total.

You should drink lots of water during Valacyclovir treatment.

You should expect Valacyclovir to reduce the duration of the cold sore by about 1 day.

Start treatment at the first sign of a cold sore for the best results.

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