Merck (MRK) Stock After Hours Today (Dec. 22, 2025): Why Shares Jumped and What to Watch Before Tuesday’s Open
Merck & Co. (NYSE: MRK) is ending Monday’s session with fresh momentum—and investors heading into Tuesday’s open (Dec. 23, 2025) have a lot to digest. After a strong regular-session rally, Merck stock closed at $104.72, up $3.63 (+3.59%), and traded slightly lower in after-hours at about $104.69 as of early evening. The day’s range ran from $100.40 to $104.95, putting MRK within roughly 1% of its 52-week high ($105.84)—a level traders will be watching closely into the holiday-shortened week. Investing.com+2Finviz+2 Merck stock price recap: the key numbers after the bell Here are the most important MRK data points investors are