Famciclovir (Famvir) Dosages for Adults: Your GoodRx Guide

If you’ve experienced cold sores, genital herpes, or shingles you know how painful they can be. So it’s good to know when to seek treatment and what you can do to make it as effective as possible.

Famciclovir (Famvir) is an antiviral medication that treats these conditions. It’s FDA approved for adults 18 years and older, but it’s not approved for children. Below, we’ll review the recommended famciclovir dosages. Keep in mind, your prescriber may recommend a different dosage for you. It’s best to follow your medical team’s instructions and speak to them if you have any questions.

What’s the typical famciclovir dosage for adults?

The typical famciclovir dosage depends on what you’re taking it for and what other health conditions you have. But for any use, it’s best to start treatment as soon as symptoms appear.

You can take famciclovir with or without food. And your prescriber may also recommend a topical medication to use along with it.

Cold sores (herpes labialis)

For cold sores, the usual famciclovir dosage is 1,500 mg by mouth as a single dose. It's best to take this medication at the first sign of a cold sore, such as tingling, redness, or itching near your mouth.

Keep in mind that famciclovir doesn’t prevent you from spreading the virus that causes cold sores (herpes simplex virus). So it’s best to avoid sharing any items that go in or near your mouth, including cosmetics. You should also avoid kissing and sexual activity until your cold sore is completely healed.

Good to know: Famciclovir comes in 125 mg, 250 mg, and 500 mg tablets. So you’ll need to take more than one tablet in order to reach a 1,500 mg dosage. You should take all of the tablets (one by one) at the same time. Don’t spread them out over the course of the day.

Genital herpes

You can take famciclovir to both treat and prevent genital herpes outbreaks.

The recommended famciclovir dosage for your first outbreak of genital herpes is 250 mg three times a day for 7 to 10 days.

For any genital herpes outbreaks after your first one, the typical famciclovir dosage is 1,000 mg by mouth twice daily for 1 day. You should start taking famciclovir as soon as possible after the first signs of an outbreak, such as burning, tingling, or blisters in the genital area.

To prevent new outbreaks, the usual famciclovir dosage is 250 mg twice a day. You’ll need to take famciclovir every day at this dosage to prevent future outbreaks — it’s not just one dose.

Keep in mind: Famciclovir doesn’t prevent the spread of herpes to others. And you can spread genital herpes even if you don’t have symptoms or open sores. So it’s best to inform your partner and use a barrier form of protection (such as a condom), even if you're taking famciclovir.

Shingles (herpes zoster)

The typical famciclovir dosage for treating shingles is 500 mg every 8 hours for 7 days. You should start it no later than 72 hours (3 days) after your shingles symptoms start.

Good to know: Shingles is contagious even if you’re taking famciclovir. So keep your rash covered and avoid direct skin contact with other people until your rash has crusted over and healed.

Are there any dosage adjustments for health conditions?

You may need a different famciclovir dosage if you’re living with HIV or you have kidney problems.

Adults living with HIV

If you’re living with HIV, the recommended famciclovir dosage for repeated genital herpes or cold sore outbreaks is 500 mg by mouth twice daily for 7 days. There isn’t a different dosage recommended for preventing herpes outbreaks or for treating shingles.

Dosage for people with kidney problems 

If you have kidney problems, you may need a lower famciclovir dosage. Your prescriber will adjust your dose based on your kidney function. So be sure to let them know if you have a history of kidney issues before you start taking famciclovir.

What happens if you miss a dose of famciclovir?

If you miss a dose of famciclovir, take it as soon as you remember. But if it's close to the time for your next dose, skip the missed dose and continue with your regular schedule. Do not double your dosage to make up for the missed one.

What should you do if you take too much famciclovir?

Taking too much famciclovir is unlikely to cause serious problems. You may experience more side effects, such as nausea or diarrhea. But it isn’t likely to be dangerous to your health.

If you or a loved one take too much famciclovir, contact your prescriber or call Poison Control at 1-800-222-1222. They’ll advise you on next steps based on how you’re feeling.

How to save on famciclovir

Famciclovir is only available as a generic medication. The brand name, Famvir, has been discontinued by the manufacturer.

GoodRx can help you save over 80% off the average retail price of the generic version. Generic famciclovir’s price at certain pharmacies is as low as $18.48 with a free GoodRx discount.

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Written by:

Alex Evans, PharmD, MBA

Alex Evans, PharmD, MBA, has been a pharmacist for 12 years. His first job was floating in a community chain pharmacy.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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