Derry 0-19 1-16 Louth
A stoppage-time point by Darren Clarke secured a draw for Louth and left Derry still not sure of Division Two safety.
After six unanswered points in the second half, four of them from the boot of Paddy Bradley, John Brennan's Derry looked set for a valuable victory.
Injury-time points by Brian White and top scorer Clarke, who finished with a goal and seven, levelled the game.
After Clarke's early goal, five points from Conleth Gilligan steered Derry to a 0-11 to 0-8 interval lead.
"We threw away a four-point lead," admitted Derry's star forward Bradley.
"Now we will find out a lot about ourselves in the last match at Westmeath.
"If we had won here today, that might have been a dead rubber, but we just did not kill Louth off when we had the chances.
"It came back to haunt us, although Louth were awarded a point which we felt was a blatant wide.
"We expect to go to Westmeath and get the win and stay in Division Two."