DEERFIELD, Ill. — Walgreen Co. is one of the latest additions on an expanding list of large employers that are attempting to control costs by having employees shop for health care coverage in a private marketplace.

Walgreen Co. is one of the latest additions on an expanding list of large employers that are attempting to control costs by having employees shop for health care coverage in a private marketplace.

The chain said that, beginning in 2014, it will give employees a set amount of money to choose health insurance coverage from a range of offerings in a rapidly growing private online marketplace run by Aon Hewitt, a benefits firm.

Walgreens joins Sears Holding Corp. and other firms in pushing its workforce into the private exchanges, part of what employee benefit analysts characterize as an historic shift in health care benefits accompanying the implementation of the Affordable Care Act, popularly known as Obamacare.

But some analysts caution that the new approach is not without potential pitfalls. For instance, although the new health care law requires large employers to provide insurance plans that are affordable for workers or face a cash penalty, the level at which firms such as Walgreens will continue to subsidize employees’ health care plans is unclear.

An estimated 160,000 workers will be impacted by Walgreens’ decision.