Walgreen Co. will fill prescriptions at no upfront cost to some patients who don’t have all the information they need for coverage received through the health care overhaul.

The nation’s largest drugstore chain said Monday evening that it will provide up to a 30-day supply of some branded and generic medicines to patients who can confirm their enrollment through the overhaul’s public insurance marketplaces but have yet to receive a plan identification number, which is normally needed to process a claim.