HMOs also manage care through utilization review. The amount of utilization is usually expressed as a number of visits or services or a dollar amount per member per month (PMPM). Utilization review is intended to identify providers providing an unusually high amount of services, in which case some services may not be medically necessary, or an unusually low amount of services, in which case patients may not be receiving appropriate care and are in danger of worsening a condition. HMOs often provide preventive care for a lower copayment or for free, in order to keep members from developing a preventable condition that would require a great deal of medical services. When HMOs were coming into existence, indemnity plans often did not cover preventive services, such as immunizations, well-baby checkups, mammograms, or physicals. It is this inclusion of services intended to maintain a member's health that gave the HMO its name. Some services, such as outpatient mental health care, are often provided on a limited basis, and more costly forms of care, diagnosis, or treatment may not be covered. Experimental treatments and elective services that are not medically necessary (such as elective plastic surgery) are almost never covered.

Other methods for managing care are case management, in which patients with catastrophic cases are identified, or disease management, in which patients with certain chronic diseases like diabetes, asthma, or some forms of cancer are identified. In either case, the HMO takes a greater level of involvement in the patient's care, assigning a case manager to the patient or a group of patients to ensure that no two providers provide overlapping care, and to ensure that the patient is receiving appropriate treatment, so that the condition does not worsen beyond what can be helped.

HMOs often shift some financial risk to providers through a system called capitation, where certain providers (usually PCPs) receive a fixed payment per member per month and in return provide certain services for free. Under this arrangement, the provider does not have the incentive to provide unnecessary care, as he will not receive any additional payment for the care. Some plans offer a bonus to providers whose care meets a predetermined level of quality.

Some critics regard HMOs as monopolies that distort the market for health care. They argue that HMOs were supposed to be a stopgap solution, and perhaps even set up for ultimate failure so the public would demand that the federal government would take over with a national health care sysem.