The International Skating Union says the 17-year-old Nagalati was negligent in relying on a doctor lacking experience of anti-doping rules who prescribed furosemide to treat swelling on her face and body.
The ruling states Nagalati "had forgotten that furosemide is on the (World Anti-Doping Agency) prohibited list."
Still, the ISU disciplinary panel said her explanation "seems to be credible" and declined to impose a two-year ban. Nagalati's suspension expires on Sept. 13.
WADA can challenge the judgment at the Court of Arbitration for Sport.
Nagalati and her partner Maxim Bobrov were disqualified from their third-place finish at the competition in Slovakia.