The Affordable Care Act may increase the number of people getting tested for HIV by nearly 500,000 by 2017.

People are much less likely to engage in risky sexual behavior if they know that they are HIV-positive. Unfortunately, more than 18 percent of people living with HIV/AIDS in the United States are unaware of their HIV status, and about half of new HIV infections are transmitted from that "HIV unaware" population. For these reasons, HIV testing is at the forefront of HIV prevention strategies in the United States. The Affordable Care Act (ACA) may support these strategies, since gaining coverage increases the likelihood of being tested for HIV. We modeled the impact of the ACA on HIV testing, diagnoses, and awareness of being HIV-positive, assuming that only the eighteen states (and the District of Columbia) that had committed to expand Medicaid as of July 2013 did expand the program. We found that the ACA will result in an additional 466,153 people's being tested for HIV and 2,598 new diagnoses of HIV by 2017. Among people living with HIV/AIDS who gain insurance through the ACA, the share of the HIV unaware will decline by 22 percent. The impact on both HIV testing and new diagnoses would be nearly 30 percent larger if all fifty states expanded Medicaid. Policy makers should consider such epidemiological benefits when analyzing insurance expansion policies.