CHICAGO (CBS)– A top-ranked U.S. rhythmic gymnast from Libertyville will be sidelined for six months after she tested positive for a banned substance.

Laura Zeng competed in the 2016 Olympics in Brazil.

Olympian Laura Zeng (WBBM/Lisa Fielding)

Zeng, 19, tested positive for a banned diuretic and a masking agent.

She said it was from an altitude sickness medication prescribed to her parent.

She claims she took it when she got sick after mistaking it for ibuprofen.

Zeng swept the gold medals in September in Peru at the Pan American Championships, a top-level international sports competition.