When should I start taking medicine for cold sores?

For repeat cold sores, the first warning sign may be tingling, itching, or burning before a blister appears. If your physician prescribed medicine to use at these signs, follow those instructions. Antiviral treatment may shorten an outbreak when started early. Results vary. Starting after a sore has fully developed may offer less benefit.

Your dose and schedule depend on the medicine, your age, kidney function, and other health details. Some cold sore treatment courses are brief, but you should not choose a schedule yourself. Read the pharmacy label and ask the pharmacist or prescribing physician if the timing is unclear. Do not double a dose or extend treatment without advice.

If you get repeated outbreaks, ask whether keeping a prescribed supply on hand is appropriate. Check its expiration date and storage instructions. If you missed the early window, contact your clinician rather than taking extra medicine. A first outbreak, unusual symptoms, or sores that keep worsening may need a fresh review instead of your usual treatment plan.