According to the anti-doping organization Wada, a banned substance has been found in her body, writes Reuters.
The Ukrainian, one of the top players in the young generation born in the 2000s, has already won three titles on the WTA Tour and is ranked 29th in the world despite a heavy finish last season.
Last year, she played against Caroline Wozniacki, Garbine Muguruza, Naomi Osaka and Simona Halep, among others.
Before Christmas, Yastremska arrived in Doha and was tested negative for covid-19, only to be infected two days later.
"The symptoms were really weird and I felt really bad," Yastremska wrote on Instagram, posting a picture of herself with a mouth guard.
She also thanked her Ukrainian doctors for helping her through the process of recovery.