Using "purchased" or forged medical certificates is illegal. For a document to be valid, it must be issued by a licensed medical facility, signed by a doctor, and stamped with the clinic's official seal.
Depending on the specific type of certificate you need (e.g., school absence, work sick leave, or fitness for driving), you can find official templates and guidance at the following sources: Common Medical Certificate Forms blank spravki bolnogo skachat
Searching for medical certificates (spravka) often leads to unreliable or unofficial sites. For legitimate, "full feature" blank medical forms used in Russia, you should refer to official legal databases or health service providers. Using "purchased" or forged medical certificates is illegal