Retail clinics recorded 5.1 million visits in 2011.
Most are located in retail drug stores and grocery stores.
More than one in three consumers are receptive to the retail clinic model, and baby boomers are especially interested.
Millennials are the least likely to use a retail clinic.
Nurse practitioners or physician assistants usually staff the clinics with varying oversight by physicians, depending on state law.
Top brands include: MinuteClinic by CVS; Healthcare Clinic by Walgreens; Target Clinic by Target; as well as several hospital-system and independent brands.
Most clinics are open seven days a week and have contracts with insurance carriers.