Valtrex (Valacyclovir): a practical guide

Valtrex (active ingredient valacyclovir) is an oral antiviral many doctors use for cold sores, genital herpes and shingles. It turns into acyclovir in your body and stops the virus from copying itself. That short step makes outbreaks milder and shorter when you start treatment early.

When to take it and typical dosing

Timing matters. For cold sores, starting Valtrex at the very first tingle helps the most. A common episodic dose for cold sores is 2 grams taken twice in one day (follow your prescriber's exact plan). For shingles (herpes zoster) doctors often use 1 gram three times daily for seven days. Initial genital herpes treatment is frequently 1 gram twice daily for 7–10 days; for recurrent episodes shorter courses like 500 mg twice daily for 3 days are used depending on your doctor’s choice. For long-term suppression, smaller daily doses (for example, 500 mg once daily) can cut outbreaks and lower transmission risk.

Safety tips, side effects and when to call your doctor

Most people tolerate Valtrex well. Common side effects include headache, nausea and occasionally dizziness. Drink plenty of water while on treatment — that lowers the chance of kidney irritation. If you have reduced kidney function, older age, or take other medicines that affect the kidneys, your dose may need adjustment. Serious problems are rare but include confusion, hallucinations or sudden decrease in urine; these require immediate medical attention.

If you’re pregnant, breastfeeding, immunocompromised, or on multiple medicines, check with your clinician before starting Valtrex. Also tell your prescriber about blood thinners, probenecid, or other regular drugs so they can check for interactions and adjust doses if needed.

Valtrex reduces symptoms and shortens outbreaks but doesn’t cure the virus. Combining suppressive therapy with safer-sex practices (condoms, avoiding sexual contact during outbreaks) lowers transmission risk further.

Want alternatives? Generic acyclovir and famciclovir are effective options depending on the situation. Topical antivirals can help some patients with cold sores. For a full rundown compare benefits, dosing and cost in our feature "Top 8 Valtrex Alternatives in 2025."

Buying and storing: keep Valtrex at room temperature, out of reach of kids. Only buy from reputable pharmacies and never share prescriptions. If a pharmacy asks for strange payment methods or offers unusually large discounts, double-check their legitimacy.

Bottom line: start treatment early, stay hydrated, follow dosing instructions, and talk to your provider about suppression if you get frequent outbreaks. If anything feels off—worsening confusion, severe rash, or signs of kidney trouble—seek medical care right away.