For sero-discordant or mixed-status couples, the possibility of HIV infection is a constant reality. There is always a risk, but you can minimize it.
If you are in a mixed-status relationship and you have sex (anal, oral, or vaginal), you can protect against HIV and other sexually transmitted infections by using condoms and dental dams consistently and correctly.
If you are part of a mixed-status couple, it is important that you and your partner communicate openly and often about safer sex practices and HIV prevention. Healthcare providers and local HIV and AIDS Service organizations can be important sources of information and support for you and your partner.
If you are the HIV-positive partner, you can lower the risk of transmitting HIV to your partner if you are on antiretroviral therapy. Taking all your medications, on time, will help to lower the viral load in your body fluids and decrease the chance that you will transmit HIV to your partner. But remember, even if you have a low viral load, you can still transmit HIV to your sex partner. So it is important to always use a condom and practice safer sex. And, if you inject drugs, never share syringes, water, or drug preparation equipment with others since HIV-infected blood can be transmitted through them. These cautions are important even if your partner is also HIV-positive. You and your partner may have different strains of HIV and cross infection could make treatment very complicated.
If you are the HIV-negative partner in a mixed-status relationship, talk with your partner about condoms and safer sex practices. If you are in an ongoing relationship with your partner, support him/her in taking all of his/her HIV medications at the right times. This "medication adherence" will lower his/her viral load and makes the risk negligible HIV can be transmitted. You may also want to stay up-to-date on developments about pre-exposure prophylaxis (PrEP) as this is an exciting addition to HIV prevention however condoms are still the only prevention that also prevents against other STIs.