LabCorp (NYSE: LH), which earlier this month was the subject of leveraged buyout rumors on Wall Street, is selling $1 billion in bonds.

The lab testing firm, which is based in Burlington, said the bonds would be sold in two $500 million packages, one with an interest rate of 2.2 percent and the other with a rate of 3.75 percent.

The bonds are expected to be sold by Thursday.

Proceeds will be used to pay off “certain amounts” of an existing credit facility and for general corporate purposes, the company said.

The company last issued bonds in November 2010, selling $325 million of 3.125 percent, 5.5-year securities and $600 million of 4.625 percent, 10-year debentures, Bloomberg data show.

The new securities are rated Baa2, the second-lowest level of investment grade, by Moody’s Investors Service.

(Bloomberg contributed to this report.)