Coady, who celebrated his 21st birthday on Tuesday, joined the Blades last summer and has scored four goals in 32 appearances, including the equaliser in the recent FA Cup victory over Nottingham Forest.
United boss Nigel Clough had no hesitation in turning Coady's youth loan into a 93-day deal, leaving the youngster available for his side's Sky Bet League One run-in.
"Conor has steadily improved throughout his time here and as a young player we are more than pleased with his progress, hence the decision to extend his stay," Clough told the club's official website.
"It was always the intention to keep him here and after his performances in the last few weeks the decision became easy, especially with Liverpool keen for him to gain further experience in our first team.
"We told him recently that we wanted to see him chipping in with more goals, then he goes and scores against Nottingham Forest and at Gillingham."