People who are eligible for Medicaid but not enrolled in the program or other source of coverage have long been considered uninsured. But some argue that this group should be considered at least partially insured because they can enroll in Medicaid if needed. To address how policymakers could best interpret counts of the more than 5 million people who are eligible for Medicaid but not enrolled, we used data from the Medical Expenditure Panel Survey Household Component to compare this group to Medicaid enrollees, Medicaid-eligible people with private coverage, and two low-income uninsured groups. Assessing differences in access to health care, use of services, and spending, we find that Medicaid-eligible but not enrolled adults have outcomes much more like those of other uninsured low-income adults and less like those of low-income adults with insurance. Our findings have policy implications for how we should interpret counts of the uninsured and highlight the importance of policies that promote Medicaid enrollment and retention.