The Nevada State Athletic Commission notified the fighters on Thursday that they will have random drug testing done, and will have to provide samples within 24-hours.
Carwin and Nelson face off at the Ultimate Fighter 16 finale in December.
The Nevada State Athletic Commission is able to randomly drug test fighters in or out of competition, similar to the testing done prior to UFC 146. The commission tested the heavyweight competitors that appeared at a press conference in Las Vegas in late March.
The results returned caused former Strikeforce heavyweight champion Alistair Overeem to be forced out of the main event against Junior dos Santos after testing positive for elevated levels of testosterone.
The commission will now be testing Carwin and Nelson as they head into their fight into December.
Former UFC heavyweight champion Shane Carwin was happy that the commission was doing the additional testing and simply said “Thank you” when reached for comment on Thursday by MMAWeekly.com.
Nelson has long lobbied for additional drug testing as well and said he would gladly do “24/7″ testing to verify he is clean of any prohibitive substances.
If similar to past tests, the results will be returned in approximately two weeks.