The 2015 women's 800m world champion Maryna Arzamasova was on Tuesday provisionally suspended after failing a drugs test, the Athletics Integrity Unit announced.
Arzamasova, 31, tested positive for LGD-4033 - an anabolic steroid-style substance banned by the World Anti-Doping Agency.
The Belarus athlete's suspension comes a month before the 2019 world championships start in Doha.
She arrived in Beijing four years ago as European 800m titleholder, adding the world title with a time of 1min 58.03sec.
Her ban was announced by the AIU on Twitter.
"The AIU confirms a provisional suspension against Belarusian middle-distance runner Marina Arzamasova for a violation of the IAAF Anti-Doping Rules," it said.
The runner's best time this year, 2min 2.51sec, is a long way shy of her personal best of 1 min 57.54 set in 2015.
She failed to make it out of the heats when trying to defend her world title in London in 2017, with Caster Semenya taking gold.