Polish tennis star Iga Świątek has accepted a one-month suspension after testing positive for a banned substance, the International Tennis Integrity Agency (ITIA) announced Thursday.

Świątek, a five-time grand slam winner, tested positive for the prohibited substance trimetazidine.

The ITIA said they found Świątek’s “level of fault was considered to be at the lowest end of the range for ‘No Significant Fault or Negligence.’”

“The ITIA accepted that the positive test was caused by the contamination of a regulated non-prescription medication (melatonin), manufactured and sold in Poland that the player had been taking for jet lag and sleep issues, and that the violation was therefore not intentional,” the ITIA said in Thursday’s statement.

The ITIA offered Świątek a suspension on November 27, which she accepted. “The player was provisionally suspended from 22 September until 4 October, missing three tournaments, which counts towards the sanction, leaving eight days remaining.

“In addition, the player also forfeits prize money from the Cincinnati Open, the tournament directly following the test,” the ITIA added.

Trimetazidine is listed as a “metabolic modulator” and its use by athletes is banned, both in and out of competition. Though it would not increase heart rate, unlike other performance-enhancing drugs that are classed as stimulants, it is believed that trimetazidine can help with endurance in physical activity.

A spokesperson for the World Anti-Doping Agency (WADA) said in a statement to CNN: “As it does with all cases, WADA will carefully review this decision by the ITIA and reserves the right to take an appeal to the Court of Arbitration for Sport, as appropriate.”

The No. 2 ranked women’s tennis player said she was shocked by the positive test.

“It was a blow for me, I was shocked and this whole situation made me very anxious. At first I couldn’t understand how that was even possible and where it came from,” Świątek said in a video posted to social media Thursday.

The 23-year-old said she instantly cooperated with the ITIA and started running tests on nutritional supplements and medications. These tests found that melatonin was contaminated which Świątek said she takes to help sleep.

“This experience, the most difficult in my life so far, taught me a lot,” the current French Open champion added.

“The whole thing will definitely stay with me for the rest of my life, it took a lot of strength, returning to training after this situation nearly broke my heart. So there were many tears and lots of sleepless nights. The worst part of it was the uncertainty.”

Świątek concluded the video asking her fans to continue to support her.

The Women’s Tennis Association (WTA) said it fully supports the former world No. 1.

“The WTA fully supports Iga during this difficult time. Iga has consistently demonstrated a strong commitment to fair play and upholding the principles of clean sport, and this unfortunate incident highlights the challenges athletes face in navigating the use of medications and supplements,” the WTA said in a statement Thursday.

“The WTA remains steadfast in our support for a clean sport and the rigorous processes that protect the integrity of competition.

“We also emphasize that athletes must take every precaution to verify the safety and compliance of all products they use, as even unintentional exposure to prohibited substances can have significant consequences.”

Świątek has won four French Open titles in her career so far, as well as winning the US Open in 2022.