Valtrex (valacyclovir) — what it treats and how to use it safely

Valtrex is an antiviral medicine used for cold sores, genital herpes, and shingles. It’s a prodrug that turns into acyclovir in your body and stops the virus from copying itself. That doesn’t cure herpes, but it shortens outbreaks, eases symptoms, and can lower how often they happen when used long term.

Start treatment as soon as you notice symptoms. For cold sores and early shingles, taking the first dose at the first tingle or pain gives the best results. For recurring genital herpes, short courses at the first sign of an outbreak work. Some people stay on daily low-dose Valtrex to prevent repeat outbreaks and reduce transmission to partners — talk with your clinician about that option.

Typical dosages and practical dosing tips

Dosing varies by condition and kidney function. Common adult doses: for a first genital herpes episode, doctors often prescribe 1 g twice daily for 7–10 days. For recurrent outbreaks, 500 mg twice daily for 3 days is common. For shingles, 1 g three times daily for 7 days is a typical plan. Always follow the exact dose your provider gives you — kids and people with kidney disease need adjusted doses.

Valtrex can be taken with or without food. Drink plenty of fluids while on it — staying hydrated helps protect your kidneys. If you forget a dose, take it as soon as you remember unless it’s near the next dose; don’t double up. If you have reduced kidney function, ask about lower doses and more spaced dosing to avoid buildup and side effects.

Side effects, risks, and interactions

Most people only get mild side effects like headache, nausea, stomach pain, or dizziness. Serious problems are rare but include confusion, hallucinations, or severe kidney issues — these are more likely in older adults or people with kidney disease. In immunocompromised patients, rare blood disorders like TTP/HUS have been reported.

Watch out for interactions: drugs that affect the kidneys (some chemotherapy agents, aminoglycosides) or drugs like probenecid can change valacyclovir levels. Live vaccines (like the varicella vaccine) may need special timing around antiviral use. Always tell your doctor about all medicines, including over-the-counter ones and supplements.

If you’re pregnant or breastfeeding, discuss risks and benefits with your provider. Valtrex is sometimes used around delivery to lower the chance of a baby getting herpes from a mother with outbreaks, but this should be managed by your healthcare team.

Get urgent care if you have severe rash, signs of a serious allergic reaction, sudden change in urination, confusion, or strange behavior. For routine questions — dosing, prevention strategies, or drug interactions — your prescriber or pharmacist can give clear, tailored advice.

Valtrex works best when used promptly and correctly. Keep a list of your meds, stay hydrated, and check in with your clinician about long-term prevention if you have frequent outbreaks.