Valacyclovir
An oral antiviral for cold sores, genital herpes and shingles. How well it works depends almost entirely on how early it is started.
Key facts
Valacyclovir at a glance.
Used for
Herpes infections, including shingles
Results
Days; start early
Treatment commitment
Condition-specific short or suppressive course
Key precautions
Kidney function affects dosing
What is it?
Top things to know about Valacyclovir
- It is an antiviral. Valacyclovir converts to acyclovir and blocks viral replication.
- It does not cure herpes. Virus remains latent in nerve tissue.
- Regimens differ by condition. Cold sores, genital herpes and shingles use different courses.
- Early use helps. Starting promptly improves the chance of benefit.
Often used for
What Valacyclovir is used for
Cold Sores
Shortens outbreaks when started early.
Shingles
Speeds healing and reduces pain.
Genital Herpes
Treats and prevents outbreaks.
Warts
Warts come from a different virus.
Molluscum Contagiosum
Doesn't work on this virus.
HOW IT WORKS
How Valacyclovir works
Diagram explanation and sources
Becomes acyclovir: The body converts valacyclovir into an antiviral drug. Activated in infected cells: Viral and cellular enzymes make its active form. Stops viral DNA copying: Inhibits viral DNA polymerase and interrupts new DNA chains.
Valacyclovir is a prodrug of acyclovir. Viral thymidine kinase initiates phosphorylation, followed by cellular enzymes; acyclovir triphosphate inhibits viral DNA polymerase and causes DNA chain termination. Latent virus remains.
Strengths
Valacyclovir strengths
Valacyclovir tablets contain 500 mg or 1 g. These are tablet sizes, not exclusive labels for prevention versus outbreaks: both can be used in different herpes regimens. Cold sores, genital herpes and shingles use different schedules, and kidney impairment can require dose adjustment.
500 mg
1 g
Used in condition-specific treatment or suppression regimens. The tablet strength alone does not tell you how often to take it.
Some regimens require more than one tablet per dose. Follow the diagnosis-specific prescription rather than choosing by outbreak severity.
Strength sources
Forms
Valacyclovir forms
Tablet
A solid oral form. Size, coating and ease of swallowing vary by product.
How to use it
Your treatment, step by step.
How to take it
- 01
When to take it
As early as possible. That is the whole treatment strategy.
For a cold sore, at the first tingle, itch or burn, before a blister appears. For a genital recurrence, at the first sign — often a tingle or ache in the same spot each time. For shingles, within 72 hours of the rash appearing, sooner if you can. For a first genital episode, as soon as it is diagnosed.
If you get recurrences, keep a supply at home rather than waiting for an appointment through the window when it still helps.
Take it with or without food, and drink plenty of water — the drug is cleared by the kidneys. - 02
If you miss a dose
Take it as soon as you remember, unless the next dose is nearly due, and do not double up. On the short high-dose courses, particularly shingles, try not to miss any. On daily suppression, a missed day is not a problem; a run of missed days may let an outbreak through.
Monitoring & follow-up
No routine blood tests for a short course in a healthy person. For long-term suppression, some doctors check kidney function periodically, particularly in older adults or anyone with kidney disease.
Kidney function is the main thing that changes dosing. It leaves through the kidneys, so impaired function means it builds up, and the effect shows in the nervous system — confusion, agitation, hallucinations, unsteadiness or unusual drowsiness. This is uncommon, mostly with high doses and reduced kidney function, and it reverses on stopping. In an older person on shingles doses, sudden confusion is a reason to call the same day. Staying well hydrated reduces the risk.
A rare but serious blood disorder has been reported with very high doses in people with severely suppressed immune systems — advanced HIV, or after a transplant. It is not a concern at cold sore or genital herpes doses.
Side effects at normal doses are mild and uncommon — headache, nausea and abdominal discomfort. Few drug interactions, because the liver enzymes behind most of them do not process it.
What to expect
How things change over time.
Start it early
Start at the tingle, before a blister forms, with or without food.
Caught early
New blisters stop forming. A cold sore caught at the tingle sometimes never blisters at all.
Pain settles
Burning and soreness ease, and genital recurrences treated at the first sign often resolve here. A first episode is where it helps most, even started a few days in.
Healing
Blisters dry and crust; shingles pain lifts. Started within 72 hours it shortens the rash and lowers the risk of lasting nerve pain.
Skin recovers
The rash heals. Shingles can leave color change or scarring.
On suppression
Its most effective use. Most people see a large drop in outbreaks, and many have none at all. Daily suppression roughly halves the chance of passing genital herpes on; condoms and avoiding contact during outbreaks still matter.
- First dose
- Hours 0 to 24
- Days 1 to 3
- Days 3 to 7
- Weeks 1 to 4
- Ongoing
When you stop
No withdrawal and no taper. Short courses simply end.
Stopping daily suppression is different. The virus has been dormant, not eliminated, so outbreaks return to their old pattern. There is no rebound — they do not come back worse — but they do come back.
Outbreak frequency tends to fall on its own over the years, so suppression is reviewed about once a year. A common approach is to stop, watch for a few months, and restart if the pattern is still troublesome. Nothing is lost; the drug works just as well the second time.
What it Pairs with
Valacyclovir + your routine
| Product or situation | With Valacyclovir | What to know |
|---|---|---|
| Waiting to see if it develops | Avoid | The window is at the start. Waiting past it wastes the course. |
| Not having a supply at home | Avoid | Getting an appointment usually takes longer than the useful window. |
| Letting yourself get dehydrated | Avoid | The drug is cleared by the kidneys, which matters most on the higher shingles doses and in older adults. |
| Touching a cold sore and then your eyes | Avoid | Herpes infection of the eye is serious and needs urgent care. |
| Close contact while a rash is blistered | Avoid | That means newborns, pregnant people who have not had chickenpox, and anyone whose immune system is suppressed. The fluid is infectious. |
| Assuming an outbreak-free stretch is safe | Avoid | Genital herpes can be shed from the skin without visible symptoms, which is why suppression lowers but does not remove the risk. |
| If you have kidney disease or reduced kidney function | Use care | Every dose is adjusted for it, so say so before you start. |
| If you are over 65 | Use care | Doses may be lowered, and confusion or unsteadiness during a course needs reporting the same day. |
| If your immune system is suppressed | Use care | HIV, chemotherapy, a transplant, or immune-suppressing medication. Doses and courses differ, and outbreaks need closer attention. |
| If a shingles rash is near your eye | Use care | Eye pain or changed vision counts too. Urgent care, not a routine appointment. |
| If a herpes rash spreads across eczema | Use care | Especially with fever. Eczema herpeticum needs same-day treatment. |
| If you are pregnant or breastfeeding | Use care | Planning a pregnancy counts too. Ask the doctor managing it, since genital herpes late in pregnancy is managed specifically. |
| If you become confused or unsteady | Use care | Seeing things during a course counts too. Stop and get in touch the same day. |
| If outbreaks break through suppression | Use care | The dose or the diagnosis may need revisiting. |
Side effects & when to get help
One of the better-tolerated drugs in dermatology. The main thing is drinking enough water, especially at the higher shingles doses.
Common
Headache
Nausea
Stomach pain
Tiredness
Tell your doctor
Less urine than usual, or swelling: Drink plenty of water while you take this.
Any kidney problem you already have: The dose is lowered for it.
Unusual drowsiness or confusion: More likely in older people.
Stop and get care
Confusion, hallucinations or slurred speech: Uncommon, and mostly with kidney problems or in older people.
Barely passing urine
Unexplained bruising or bleeding: Very rare, but serious.
Getting it and cost
Getting Valacyclovir.
Cost & access
Generic valacyclovir is inexpensive and widely stocked. The brand costs far more and offers nothing extra.
What affects the cost
Daily suppression costs more over a year simply because it is taken daily, but 500 mg tablets are among the cheaper generics.
What affects the cost
Aciclovir tablets are cheaper still and work just as well, but they have to be taken up to five times a day, which is why valacyclovir is usually prescribed instead. If cost decides it, ask about aciclovir.
What affects the cost
Some insurers limit how many tablets can be dispensed for episodic treatment, which conflicts with keeping a supply at home. Raise it with the prescriber directly.
Alternatives
Other options to consider.
Aciclovir
the same drug in a less absorbable form, and considerably cheaper. Just as effective if taken as prescribed, but needs three to five doses a day rather than one to three.
Famciclovir
comparable results and similar dosing convenience. Usually costs more than generic valacyclovir, and is a reasonable alternative if one is not tolerated.
Topical aciclovir or penciclovir cream
much less effective than tablets for cold sores. Reasonable for someone who cannot take tablets, and applied five times a day.
Docosanol cream, sold over the counter
a small reduction in cold sore duration. Available without a prescription, which is its main advantage.
The shingles vaccine
not a treatment, but the better answer for anyone eligible. It prevents most cases of shingles and reduces the severity of those that still occur.
Nerve pain treatment after shingles
valacyclovir treats the virus, not established nerve pain. Pain that persists after the rash heals is managed with specific medicines for nerve pain rather than more antiviral.
Questions
Questions you might be asking.
When exactly should I take it for a cold sore?
At the first tingle, itch or burn, before any blister appears. That is when the one-day course does most.
Does it cure herpes?
No. The virus stays dormant in nerve tissue permanently. It shortens outbreaks, prevents most while taken daily, and lowers transmission risk.
Will taking it daily stop me passing it to my partner?
It roughly halves the risk — a large reduction, not elimination. Condoms and avoiding contact during outbreaks still matter.
Why is shingles treated so urgently?
The benefit depends on starting within about 72 hours — then it shortens the illness and lowers the risk of lasting nerve pain.
Can I drink alcohol on it?
There is no direct interaction. Staying hydrated matters more.
Do I have to take it forever?
No. Suppression is reviewed about once a year. Outbreaks become less frequent over time, and many people stop and find they do not need it.
Related
Keep exploring.
Shingles
Cold Sores
Molluscum Contagiosum
Warts
Shingles vs Cold Sores
Shingles vs Folliculitis
Shingles vs Contact Dermatitis
Shingles vs Chickenpox
Cold Sores vs Impetigo
Cold Sores vs Allergic Contact on Lips
Cold Sores vs Canker Sores
