The company, based in Deerfield, Ill., said Thursday that most of its 370 in-store Take Care Clinics now will diagnose, treat and monitor patients with some chronic conditions that are typically handled by doctors.

These clinics, which are run by nurse practitioners or physician assistants, have grown popular in recent years as a convenient and less expensive way to treat relatively minor illnesses when a patient doesn't have a doctor or if their physician isn't available. But the clinics have been broadening their scope of care: Walgreen's decision follows a move by competitor CVS Caremark Corp. a few years ago to start monitoring chronic conditions at most of its 640 MinuteClinics.

Drugstores say they don't aim to replace doctors, but rather to provide more people with access to health care and to work with physicians as part of a team treating patients. But the move to provide more complex care draws concern from doctors who say that can disrupt their relationships with patients and lead to fragmented care.