To increase HIV testing, in 2008 California's governor signed the first piece of legislation in the USA to require private health plans to cover the cost of HIV testing regardless of whether testing is related to a primary diagnosis. This study assesses the impacts of the bill on insurance coverage, testing rate, and cost for 22,190,000 Californians. The law addresses the major public health challenge presented when people who aren't aware they have HIV unwittingly transmit the infection and delay treatment. 

Findings: Most of the 22,190,000 privately insured Californians already have coverage for HIV testing, and the authors found if those who previously paid out-of-pocket for tests were now covered, the increased cost for could be as low as $554,000 in 2009 when the law took effect. But even if guidelines proposed by the Centers for Disease Control and Prevention to screen widely for HIV are fully adopted, costs to insurers are expected to be small, about $10 million a year or 0.013% of total private health insurance expenditures in California. This policy change could serve as an important step toward making HIV testing a routine screening testing.