Paul McVeigh's last-gasp penalty gave Donegal Celtic a vital point in their battle against Premiership relegation.
United's Neil McCaffery missed a penalty before Ryan Henderson fired DC ahead.
Aaron Boyd levelled and the visitors moved 3-1 in front after Eamonn Murray and Gary McCutcheon goals.
Henderson pulled one back before McVeigh's penalty two minutes into injury-time after Gary Haverson was red-carded for a foul on Henderson.
Ballymena had the better chances and Murray struck the woodwork before McCafferty saw his weak penalty easily saved.
It looked over for Donegal Celtic after McCutcheon's superb 82nd minute strike but Henderson nipped in to equalise within 60 seconds and McVeigh's late spot-kick sealed the point.
The draw takes the west Belfast side six points clear of basement side Newry, who lost 1-0 at Dungannon Swifts.
"To come back from 3-1 down with less than 10 minutes left shows a lot of character," said Donegal Celtic boss Paddy Kelly.
"However, although we have character in abundance we need to improve our performances."