Condition-specific schedules
Valtrex Dosage: Label Schedules and Safety Factors
Valtrex dosage is condition-specific: cold sores, genital herpes, suppression, transmission reduction, and shingles use different label schedules. Kidney function, age, immune status, pregnancy, timing, and interacting medicines can change the prescribing decision.
Valtrex dosage depends on the condition being treated, whether an episode is initial or recurrent, age, immune status, and kidney function. The schedules below summarize the current U.S. prescribing label for valacyclovir. They are educational, not a personal prescription. A licensed clinician must select and adjust the regimen for an individual patient.
Medically reviewed
Infectious-disease specialist · antimicrobial stewardship and medication safety
Reviewed August 27, 2026
Valtrex dosage by condition and renal function
Use this matrix to locate the right condition before reading the detailed safety and renal-adjustment sections.
| Use | U.S. label schedule | Start point | Clinician check |
|---|---|---|---|
| Cold sores | 2 g, then 2 g 12 hours later; one day only | Earliest tingling, itching, or burning | Diagnosis, age, renal function |
| Initial genital herpes | 1 g twice daily for 10 days | As early as possible after symptoms | First episode, testing, immune status |
| Recurrent genital herpes | 500 mg twice daily for 3 days | First sign or symptom | Confirmed recurrence, renal function |
| Shingles | 1 g three times daily for 7 days | Earliest sign or symptom | Rash location, immune status, kidneys |
Schedules summarized from the January 2026 FDA-approved Valtrex label. A prescriber selects and adjusts the regimen.
A safer dosing check in four steps
- Name the indication.Cold sores, genital herpes, and shingles use different schedules.
- Confirm the treatment goal.An acute episode and long-term suppression are not interchangeable.
- check renal risk.Kidney disease, dialysis, older age, dehydration, and nephrotoxic medicines may require adjustment.
- Plan for timing problems.Know when to start, what to do after a missed dose, and who to call if symptoms worsen.
Prescription status: Valtrex is a prescription medicine in the United States. Do not start, stop, split, or change a dose based only on an online summary.
Valtrex dosage schedules in the U.S. label
The January 2026 FDA-approved Valtrex prescribing information on DailyMed lists different adult regimens for cold sores, genital herpes, and herpes zoster. The label states that Valtrex may be taken without regard to meals. Timing matters because each condition has a different recommended point for starting treatment.
- Cold sores: 2 grams twice in one day, with the doses taken 12 hours apart. The label says treatment should begin at the earliest symptom, such as tingling, itching, or burning.
- Initial genital herpes: 1 gram twice daily for 10 days. The label notes that treatment was most effective when started within 48 hours after signs or symptoms began.
- Recurrent genital herpes: 500 mg twice daily for 3 days, started at the first sign or symptom of an episode.
- Suppressive genital herpes therapy: the label includes daily regimens that vary with immune status and recurrence history. This choice requires clinician check rather than self-selection.
- Herpes zoster (shingles): 1 gram three times daily for 7 days. The label advises starting at the earliest sign or symptom and reports the greatest effectiveness when treatment begins within 48 hours after the rash starts.
These are labeled schedules, not a recommendation that every reader should receive Valtrex. See the focused explanations for cold-sore dosing and timing, genital-herpes treatment and suppression, and shingles dosing considerations.
Why a clinician may adjust the labeled schedule
Kidney function is a central dosing factor. The label provides reduced regimens for adults with impaired renal function and advises caution in older adults, people with underlying renal disease, people taking potentially nephrotoxic medicines, and anyone who is not adequately hydrated. Dialysis timing and the severity of renal impairment can also affect the plan.
Age and immune status matter as well. The adult schedules cannot simply be copied for a child. The label includes a cold-sore regimen for adolescents aged 12 years and older, but pediatric use for other conditions follows different evidence and limitations. People with advanced HIV infection, transplant history, pregnancy, or other complex medical circumstances need individualized check before treatment.
Interactions, contraindications, and side effects
The label states that no clinically significant drug-drug or drug-food interactions with Valtrex are known. That does not make a medication check unnecessary. Medicines that can affect the kidneys, dehydration, renal disease, and dosing above the renal-adjusted recommendation can increase risk. Give the prescriber and pharmacist a complete list of prescriptions, over-the-counter products, and supplements.
Valtrex is contraindicated for a person with a clinically significant hypersensitivity reaction to valacyclovir, acyclovir, or a formulation component. Common adult adverse effects described in the label include headache, nausea, and abdominal pain. Serious warnings include acute renal failure, central nervous system reactions such as confusion or hallucinations, and severe skin reactions.
When to contact a clinician promptly
Seek urgent medical help for a painful or progressive rash, mouth sores, blistering or peeling skin, breathing difficulty, facial swelling, seizure, severe confusion, hallucinations, or markedly reduced urination. Contact the prescriber if symptoms worsen, the diagnosis is uncertain, a dose was taken incorrectly, or the course cannot be followed as written.
Common dosing mistakes to avoid
- Using a schedule written for a different herpes condition.
- Treating a first genital episode like a recurrent episode.
- Ignoring kidney disease, dehydration, age, or dialysis.
- Doubling the next dose after a missed dose.
The patient labeling says to take a missed dose when remembered unless it is almost time for the next one, and never to take two doses together or more than prescribed. The missed-dose steps explains how to apply that instruction without calculating a replacement schedule.
Questions to settle before prescribing
Ask which diagnosis the prescription treats, whether the plan is for one episode or ongoing suppression, and what to do if symptoms begin outside clinic hours. Confirm the exact tablet strength, renal instructions, hydration advice, and the contact route for side effects or a dosing error. These practical details prevent a correct label schedule from being applied to the wrong situation.
Access and follow-up
A prescription decision should connect the diagnosis, treatment goal, kidney function, other medicines, and the ability to start at the right time. If a clinician decides Valtrex is appropriate, check the medication label and pharmacy instructions together. For the clinical evaluation and pharmacy process, see the Valtrex prescription access page.
This information is educational and does not replace medical advice, diagnosis, or a prescription from a licensed clinician.
Common questions
Can Valtrex be taken with food?
The U.S. label states that Valtrex may be taken without regard to meals. Follow the pharmacy directions and ask if nausea makes the schedule difficult.
Does every adult receive the same schedule?
No. The indication, treatment goal, kidney function, age, immune status, and timing can change the prescribed regimen.
Can a dose be adjusted by splitting tablets?
Do not invent a renal or condition-specific adjustment. Use the exact tablet strength and interval selected by the prescriber.
What if a dose is missed?
Take it when remembered unless the next dose is almost due. Never double the next dose or take more than prescribed.