Drugmaker Eli Lilly plans to lay off about 1,000 domestic sales representatives, or 30% of its U.S. sales force, as it faces new generic competition for its top drugs, a person familiar with the matter said on Friday.

The cuts include both full-time and contract sales employees. Lilly has 38,000 employees worldwide and about 17,000 in the United States.

At the same time, the company plans to add 300 people to its diabetes sales force, the source said.

Lilly confirmed in a statement that it is restructuring its sales force to adapt to changes including the expiration of two patents, and said it would expand its diabetes sales force. The news was first reported by the Associated Press and other outlets.

Drug companies often reduce the sales force when their patents expire and cheaper generics are introduced to the market.

Lilly's profit fell 6% last year after it lost its U.S. patent protection for top-selling schizophrenia drug Zyprexa. Cost controls helped keep those losses from being worse.

At the end of 2013 the Lilly antidepressant Cymbalta will lose patent protection, and copycat forms of the company's $1 billion-a-year Evista osteoporosis drug are due to arrive in early 2014. The company has forecast flat sales for 2013.

During the fourth quarter, the Indianapolis-based drugmaker took a charge of $64.7 million for global restructuring, which included an unspecified number of layoffs.

In January Lilly forecast aggressive, companywide cost controls this year.