The 2010 Affordable Care Act extended dependent coverage for adult children up to age 26 in the USA. Since then, considerable studies have assessed its various impacts among young adults. However, little is known about whether there is any change in health care use when young adults age out of dependent coverage. This study examines health care consumption changes among young adults prior to their aging out process. I used data from a large insurance claim database and studied health care utilization of young adults under parents' coverage during a 2‐year period in a difference‐in‐difference framework. I found that young adults had relative reductions in health services use, except ER visits, compared with individuals who stayed under parents' coverage. This pattern was the same for both male and females. Individuals with regular medical needs had greater relative reductions compared with those without regular medical needs. The relative reductions in health care use during the aging out process may have an important impact on young adults' health, especially for those with regular medical needs. More efforts could be made to help them maintain regular medical utilization during the transition.