Nabokau's suspension comes less than a month after the world championships ended in early October.
At the worlds in Doha, the 23-year-old Belarusian cleared 2.26 metres in qualifying but was later eliminated.
The AIU, which oversees integrity issues in international athletics, including doping, said Nabokau had tested positive for furosemide, which is on the World Anti-Doping Agency's list of prohibited diuretics and masking agents.
It did not say when the sample had been taken.
Nabokau, who competed at the 2016 Summer Olympics, won silver at the world junior athletics championships in 2014. (Reporting by Gabrielle Tétrault-Farber Editing by David Holmes)