Five-time Grand Slam champion Iga Swiatek accepted a one-month suspension after testing positive for the banned substance trimetazidine, a heart medication known as TMZ, the International Tennis Integrity Agency announced Thursday.

Swiatek failed an out-of-competition drug test in August. She formally admitted the anti-doping rule violation Wednesday and accepted her penalty. The ITIA accepted her explanation that the result was unintentional and was caused by the contamination of a nonprescription medication, melatonin, that Swiatek was taking for issues with jet lag and sleeping.

It was determined her level of fault was “at the lowest end of the range for no significant fault or negligence,” the ITIA said.

Swiatek has only eight days remaining on the punishment, after she was provisionally suspended from Sept. 12 to Oct. 4 and missed three tournaments. The remaining suspension will be completed while there is no competition, and Swiatek will be cleared to return to play as of Monday.

She had said in September that she was missing the Korea Open, China Open and Wuhan Open for personal reasons.

The ITIA said Swiatek also forfeited her prize money of $158,944 from the Cincinnati Open, the first tournament she played after the failed test. Swiatek lost in the semifinals in Cincinnati.

Swiatek, 23, called testing positive the “worst experience of my life.”

“In the last 2½ months, I was subject to strict ITIA proceedings, which confirmed my innocence,” Swiatek said in an Instagram video. “The only positive doping test in my career, showing unbelievably low level of a banned substance I’ve never heard about before, put everything I’ve worked so hard for my entire life into question.

“Both me and my team had to deal with tremendous stress and anxiety. Now everything has been carefully explained, and with a clean slate I can go back to what I love most.”

This is the second recent high-profile doping case in tennis. Jannik Sinner failed two tests for a steroid in March and was cleared in August, right before the start of the US Open, which he went on to win for his second Grand Slam title of the season.

Swiatek, from Poland, was ranked No. 1 most of the past two seasons but is now at No. 2. She won the French Open in June for her fifth major championship and took home a bronze medal at the Paris Olympics in early August.

She was passed for the top spot by Aryna Sabalenka during her provisional suspension.

The WTA said in a statement that it “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.

TMZ is the drug at the center of the case involving 23 Chinese swimmers who remained eligible for the Tokyo Olympics despite testing positive for performance enhancers in 2021. Russian figure skater Kamila Valieva also tested positive for TMZ, with the result revealed during the 2022 Winter Olympics. She was disqualified from the team competition at the Beijing Games and handed a four-year doping ban.

The Associated Press and Reuters contributed to this report.