Abbott Laboratories is buying Alere for $5.8 billion as it tries to expand its medical diagnostics business.
Alere makes tests used to diagnosis the flu, HIV, malaria and several other diseases, while Abbott makes drugs, infant formula and medical devices.
Abbott said Monday that it will pay $56 for each share of Alere, a 50 percent premium from Friday's closing price of $36.20.
Shares of Alere Inc., based in Waltham, Massachusetts, jumped more than 45 percent in premarket trading. Shares of Abbott Laboratories, based in Abbott Park, Illinois, rose less than 1 percent before the stock market open.