Why did Tandem Diabetes Care stock go down today?
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Shares of Tandem Diabetes Care (NASDAQ:TNDM) dropped for the third straight session on Wednesday after UBS downgraded rival insulin pump maker Medtronic (NYSE:MDT) and preferred Abbott Laboratories (ABT) in the diabetes market. 
Downgrading MDT to Sell from Buy with a $79 target, analyst Danielle Antalffy projected 2% below consensus sales and 3%/8% below consensus EPS for the company in FY24 and FY25.
Medtronic (MDT), Tandem (TNDM), and Insulet (PODD) offer insulin delivery systems for diabetes market which UBS thinks will grow at mid-teens, implying one of the fastest subsector growth rates in its coverage.
Citing a survey, Antalffy projects double-digit growth in the pump market, and expects new product launches to drive market share shifts. She prefers Neutral-rated Insulet (PODD) and Tandem (TNDM) over Sell-rated Medtronic (MDT).
However, in the diabetes market, the analyst picked the makers of continuous glucose monitoring systems (CGMs) DexCom (DXCM) and Abbott Laboratories (ABT) with Buy ratings, ahead of Insulet (PODD) and Tandem (TNDM).
The analyst projects continued double-digit growth for CGM devices and expects DXCM to gain market share.
In a recent industry report, Allied Market Research estimated CGM market to reach $31.7B by 2031.