** Shares of U.S. medical device makers decline between 1% and 3.5% premarket

** GE Healthcare GEHC.O and glucose monitor manufacturer Dexcom DXCM.O both decline 3% each

** President Donald Trump imposed an additional 34% tariff on China, 20% tariff on EU and 25% tariff for some goods from Canada and Mexico

** Tariffs imposed on these geographies could hurt R&D spending, availability of certain devices and cause supply chain disruptions for these device manufacturers, Citi analysts wrote in a note

** Some firms such as Boston Scientific BSX.N and GEHC have accounted for impact of tariffs in their fiscal 2025 guidance, while others such as Abbot ABT.N and DXCM have not

** Shares of medical device firms Abbott ABT.N and Boston Scientific BSX.N also fall over 1% before the bell

** As of last close, ABT up ~17%, BSX up 12% and GEHC up 1.5%, while DXCM down 12.4% YTD

** S&P 500 Health Care Equipment sub index .SPLRCMED is up 5.4% so far this year

(Reporting by Bhanvi Satija in Bengaluru)

((Bhanvi.Satija@thomsonreuters.com; Outside U.S. +91 9873062788;))