(Photo: AP)

Serena Williams has complained on social media that it’s “test Serena” time again as she once more hit out at the frequency with which she is selected for anti-doping tests.

The 23-time Grand Slam champion took to Twitter on Tuesday night after she received another visit from a tester.

Williams tweeted: “And it’s that time of the day to get ‘randomly’ drug tested and only test Serena. Out of all the players it’s been proven I’m the one getting tested the most. Discrimination? I think so. At least I’ll be keeping the sport clean.”

Serena Williams has complained on social media that it’s “test Serena” time again as she once more hit out at the frequency with which she is selected for anti-doping tests.

The 23-time Grand Slam champion took to Twitter on Tuesday night after she received another visit from a tester.

Williams tweeted: “And it’s that time of the day to get ‘randomly’ drug tested and only test Serena. Out of all the players it’s been proven I’m the one getting tested the most. Discrimination? I think so. At least I’ll be keeping the sport clean.”