The downgrade comes after the Sunnyvale, CA-based molecular diagnostics company agreed to be acquired by Danaher (DHR) last week, the Fly reports.
Danaher will pay $4 billion, or $53 per share in cash, for the company.
The deal is subject to regulatory approval, but is expected to close by the end of the year.
Danaher is a Washington, DC-based company that manufactures and markets professional, medical, industrial and commercial products and services.
Shares of Cepheid were edging lower in mid-morning trading on Monday.
Separately, TheStreet Ratings Team has a "Sell" rating with a score of D+ on Cepheid stock.
Among the areas that are negative, one of the most important has been an overall disappointing return on equity.
Recently, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author.
You can view the full analysis from the report here: CPHD