Chelsea head coach Enzo Maresca had claimed that Mudryk has been missing since the Villa game through illness.
According to the FA’s website, footballers who provide a positive ‘A’ doping sample are provisionally suspended pending the findings of their ‘B’ sample and can face a ban of four years.
In a statement posted on Instagram, Mudryk said: “I can confirm that I have been notified that a sample I provided to the FA contained a banned substance.
“This has come as a complete shock as I have never knowingly used any banned substances or broken any rules, and am working closely with my team to investigate how this could have happened.
“I know that I have not done anything wrong and remain hopeful that I will be back on the pitch soon. I cannot say any more now due to the confidentiality of the process, but I will as soon as I can.”
Chelsea released a statement that said: “Chelsea Football Club can confirm the Football Association recently contacted our player Mykhailo Mudryk concerning an adverse finding in a routine urine test.
“Both the club and Mykhailo fully support the FA’s testing programme and all our players, including Mykhailo, are regularly tested. Mykhailo has confirmed categorically that he has never knowingly used any banned substances. Both Mykhailo and the club will now work with the relevant authorities to establish what has caused the adverse finding.
“The club will not be commenting any further.”
Murdryk joined Chelsea almost two years ago in a deal worth an initial £62 million and still has seven years to run on a contract which was extended by 12 months this year.
Paul Pogba had a four-year ban for doping reduced to 18 months and subsequently had his contract terminated at Juventus.
Having joined from Shakhtar Donetsk in 2023, Mudryk has struggled with the transition to the Premier League and is yet to fulfil his promise.
He has worked with a personal trainer, Dmytro Chapovskyi, who has also been pictured with Chelsea midfielder Enzo Fernández.
Mudryk has scored five Premier League goals in 26 starts and has fallen behind Pedro Neto, Noni Madueke and Jadon Sancho in the Chelsea pecking order.
As part of his £62m ($137m) move, Chelsea agreed to a series of bonuses that could push Mudryk’s total fee above £80m ($177m).