It’s recommended that men who have sex with men test for HIV every 3-6 months.
There’s a period of time after a person is infected during which they won’t test positive. In other words, there’s a period of time when a person is HIV-positive but won’t know it yet. This is called the HIV “window period.” The window period can last between 10 days and three months, depending on the person’s body and on the HIV test that’s used. During that time, a person can test HIV-negative even though they’re HIV-positive. Someone in the “window period” of HIV infection can still transmit HIV to another person. In fact, people with very early HIV infection, who may still be in the window period of HIV infection, are actually much more infectious than later on in their infection. That’s one reason frequent testing is so important.