Halep is seeking more than $10 million in damages from Quantum Nutrition, which operates as Schinoussa Superfoods, after testing positive at the 2022 U.S. Open for Roxadustat, a drug often used by people with anaemia.
Roxadustat is on the World Anti-Doping Agency's banned substances list because it can increase haemoglobin and the production of red blood cells, building endurance.
Romanian Halep said she used Schinoussa supplements during the 2022 Flushing Meadows tournament, and that the Keto MCT she took had been contaminated with Roxadustat, which was not disclosed on the label.
The two-time Grand Slam champion said she has never used any banned substances, and that Quantum's negligence and false claims that its supplement was legal has harmed her career and caused humiliation.
Halep is also seeking punitive damages. She sued in a New York state court in Manhattan.
Quantum, based in Scarborough, Ontario, did not immediately respond to a request for comment.
Its founder told Canadian newspaper The Globe and Mail in October that Halep was seeking a scapegoat and his company was being made into "the fall guy."
Lawyers for Halep did not immediately respond to requests for additional comment.
Halep is appealing the four-year suspension imposed last September by an International Tennis Integrity Agency tribunal.
While agreeing that Halep had not known that the supplement might have contained Roxadustat, the tribunal said the contamination could not have accounted for how much of the drug was found in her August 29th, 2022 urine sample.
Halep appealed that ruling last week before the Court of Arbitration for Sport in Lausanne, Switzerland.
"I really believe that the truth is going to come out and the day to be on court is going to be soon," Halep told reporters.
Halep won the French Open in 2018 and Wimbledon in 2019.
The case is Halep v Quantum Nutrition Inc et al, New York State Supreme Court, New York County.
