Valtrex (valacyclovir): what it treats and how to use it

Valtrex is a widely used antiviral prescribed for shingles, genital herpes, and cold sores. It works by blocking viral replication, which helps symptoms heal faster and can lower the chance of spreading the virus. You need a prescription, and timing matters — starting treatment early gives the best results.

How people commonly use Valtrex

Doctors prescribe Valtrex for several situations: to treat an active genital herpes episode, to suppress frequent recurrences, to shorten a shingles episode, and to nip cold sores in the bud. For example, genital herpes suppression is often daily low-dose therapy to reduce outbreaks and lower transmission risk. Shingles treatment uses a higher dose for a short course to reduce pain and speed healing. Exact dosing depends on the condition, your kidney function, and whether this is your first episode or a repeat.

Typical doses and important warnings

Here are common dosing patterns you may see — do not change your dose without talking to your prescriber:

- Genital herpes, initial episode: commonly 1 g twice a day for 10 days. Recurrent episodes: 1 g twice a day for 5 days or 500 mg twice a day for 3 days. Suppressive therapy: 500 mg to 1 g once daily depending on frequency and doctor advice.

- Shingles (herpes zoster): often 1 g three times a day for 7 days.

- Cold sores (herpes labialis): many regimens use 2 g taken twice in one day at the first sign of an outbreak.

If you have impaired kidney function, your doctor will lower the dose. That’s critical — valacyclovir is cleared by the kidneys, and too much can cause serious problems, especially in older adults.

Common side effects include headache, nausea, and stomach discomfort. Less common but serious effects include confusion, severe kidney injury, and allergic reactions. If you notice trouble urinating, sudden swelling, severe dizziness, or new mental changes, seek medical help quickly.

Drug interactions: tell your doctor about other medicines that affect the kidneys or the immune system. Probenecid can raise valacyclovir levels. Combining with other nephrotoxic drugs increases risk to your kidneys.

Practical tips that matter:

- Start treatment as soon as possible, ideally within 48–72 hours of symptoms. Early use gives the best benefit.

- Stay well hydrated while taking Valtrex to help kidney clearance.

- Avoid sexual contact during visible genital outbreaks and until lesions fully heal; suppression lowers but doesn’t eliminate transmission risk.

- Keep a list of your medicines and bring it to appointments so your prescriber can check for interactions.

- If you’re pregnant, breastfeeding, elderly, or have kidney disease, talk to your provider about risks and dosing adjustments.

Valtrex is effective when used correctly. Follow your prescription, watch for side effects, and ask questions if dosing or timing is unclear. If symptoms worsen or you have signs of severe reaction, contact your healthcare provider right away.