World No. 2 and five-time Grand Slam champion Iga Swiatek has accepted a one-month suspension after testing positive for banned substance trimetazidine (TMZ), the International Tennis Integrity Agency said on Thursday.

Swiatek tested positive in an out-of-competition sample in August but the ITIA, which runs tennis's anti-doping program, accepted that it was caused by contamination of her medication melatonin, which was manufactured and sold over the counter in her native Poland.

Swiatek said she had been taking it for jet lag and sleep issues and as there was no significant fault or negligence, the ITIA ruled it was "the lowest end of the range" and offered the reigning French Open champion a one-month suspension which the 23-year-old accepted.

"The player was provisionally suspended from September 12 until October 4, missing three tournaments, which counts towards the sanction, leaving eight days remaining," the ITIA said in a statement.

Swiatek also forfeited prize money from the Cincinnati Open, the tournament directly following the test. Having pulled out of tournaments in Asia in September citing personal matters and fatigue, she described the ordeal of testing positive as the "worst experience of my life".

She was World No. 1 when she failed the test and having skipped the Asian swing, Aryna Sabalenka leapfrogged her in the world rankings to eventually end the year as No. 1.

"In the last two and a half months I was subject to strict ITIA proceedings, which confirmed my innocence," Swiatek said on Instagram. "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."

Swiatek, whose anti-doping violation was not made public at the time, had her provisional suspension lifted after providing samples of her melatonin product to the WADA-accredited SMRTL laboratory in Salt Lake City which confirmed detecting low doses of TMZ in both opened and sealed containers of the product.

The provisional suspension was lifted on October 4 and the case forwarded to an Independent Tribunal.