PEP is most effective when initiated as soon as possible after exposure. Completing the full prescribed course (typically 28 days) is crucial for optimal effectiveness. PEP is intended for emergency situations and is not a substitute for consistent HIV prevention strategies, such as condom use or PrEP (pre-exposure prophylaxis). A healthcare provider must evaluate the exposure risk to determine if PEP is appropriate. HIV testing is required before starting PEP and during follow-up to monitor for infection.