Valacyclovir dosage: how much and when to take it

Valacyclovir (Valtrex) is an antiviral used for shingles, genital herpes, and cold sores. Getting the dose right matters — too little won't control the virus, too much can raise side effect risk. Below are common adult dosing options you may see from a doctor.

Typical adult dosing

Shingles (herpes zoster): 1 gram (1000 mg) three times a day for 7 days. This is the standard course to shorten symptoms and reduce complications.

Initial genital herpes: 1 gram twice daily for 10 days. Treat early for the best results.

Recurrent genital herpes: either 500 mg twice daily for 3 days or 1 gram twice in one day (taken 12 hours apart) depending on the regimen your clinician prefers.

Suppressive therapy for frequent recurrences: 500 mg to 1 gram once daily — your prescriber will pick the right option based on how often outbreaks happen.

Cold sores (herpes labialis): a short course of 2 grams taken twice in one day (12 hours apart) usually controls an outbreak if started at the first sign.

Practical tips, safety, and adjustments

Start treatment as soon as you spot symptoms — for shingles and genital herpes, earlier treatment reduces severity and healing time. Take pills with or without food. Drink water; staying hydrated helps kidney clearance.

Have kidney problems? Dosing changes are often needed. Doctors check creatinine and adjust dose or spacing. Don’t self-adjust — ask your prescriber or pharmacist for the right plan.

Side effects are usually mild: headache, nausea, stomach pain, and dizziness. Rarely, serious kidney issues or confusion can occur, especially in older adults or dehydrated patients. Stop and call a doctor if you have severe weakness, sudden confusion, or very low urine output.

Interactions: valacyclovir is generally low on drug interactions, but combining with other kidney-impacting drugs (like high-dose NSAIDs or certain antivirals) raises risk. Tell your provider about all medicines and supplements.

Missed dose? If you remember soon after, take it. If it’s close to the next scheduled dose, skip the missed one — don’t double up.

Pregnancy and breastfeeding: talk to your doctor. Valacyclovir is sometimes used in pregnancy, but your clinician will weigh benefits and risks for you specifically.

Final note: these are common dosing patterns, not a prescription. Always follow the exact instructions your prescriber gives, and reach out if symptoms worsen or don’t improve within the expected timeframe.

Call your doctor if fever or spreading rash occurs, or if painful blisters don't start to heal within a week. For genital herpes, avoid sexual contact until lesions fully crust and symptoms are gone; suppressive therapy can cut transmission risk but doesn't eliminate it. If you take valacyclovir long term your clinician may check kidney function and sometimes blood counts. Traveling? Bring a copy of your prescription and store pills in original packaging. If you buy meds online, use a licensed pharmacy and confirm the product is genuine. Any sudden severe side effect—stop the drug and get urgent medical help. Ask your pharmacist any questions.