In the United States, it is to buy authentic Viagra or its generic, sildenafil, without a prescription from a licensed healthcare provider. While you may see "non-prescription" options advertised online, these are often illegal, counterfeit, or potentially dangerous supplements. The Risks of "Non-Prescription" Online Buys
Websites claiming to sell Viagra without a prescription bypass critical safety checks, which can lead to serious health and financial consequences: Buying ED Drugs Online: What's the Risk? - WebMD