Ian Harkes' acrobatic diving header hauled United level in the first halfInjury-hit Celtic's troubled start in the Scottish Premiership intensified as Dundee United held on for a point.
Liel Abada nodded Celtic ahead, but the visitors soon levelled with a terrific Ian Harkes header.
The hosts hit the woodwork three times, and Albian Ajeti missed an open goal, while United had a strong penalty claim rejected when Nicky Clark was felled.
Celtic's first dropped points at home, combined with three away defeats, leaves them in sixth place.
They are six behind leaders Rangers and one behind United whose youthful side impressed and withstood a late barrage in a breathless contest to collect their first point at Celtic Park in eight years.
Depleted Celtic's injury worries mounted with the first-half loss of full-back Josip Juranovic.
While Celtic had made their worst start to a league season in 23 years, it could be pinned on their away form which contrasted sharply with their flawless home start of three straight wins.
United halted that record and seized on Celtic's sloppiness in a frantic first half full of incident.
Celtic built early momentum - Juranovic had shot batted away by Benjamin Siegrist and Ajeti headed too high - before their wingers combined for the breakthrough. Jota jinked down the left and cut in to swing over a cross met with a thumping Abada header at the back post.
The setback galvanised United and they were back level within two minutes. Finnish winger Ilmari Niskanen outmuscled Anthony Ralston down the left and his whipped delivery was brilliantly converted by Harkes' diving header.
Both sides had reason to feel aggrieved not have a half-time lead. United - whose high press unsettled Celtic's defence throughout - were bemused by Kevin Clancy's decision not to award a penalty when Cameron Carter-Vickers sent Nicky Clark sprawling.
At the other end, Ajeti inexplicably blazed over an unguarded net from four yards and David Turnbull sent a 20-yard strike against the bar. Ajeti would be guilty of another glaring miss late in the second half, heading wide from six yards.
Ange Postecoglou's men piled on the pressure after the break, but lacked conviction in the final third.
Jota looked their best hope of a winner, and almost got it with a dripping drive off the bar in the final few minutes. Tom Rogic also shook the bar with a header from Jota's knockdown.
United, though, remained a danger on the counter-attack. They could have snatched a dramatic victory when substitute Louis Appere had a near-post drive saved by Joe Hart and it then took a superb Carl Starfelt tackle to halt the striker in a two-on-one breakaway.
More to follow.
helpHow to play
Rate players out of 10 throughout or after the game. The rater will close 30 minutes after the final whistle.
Rating range key1 = Give it up10 = Pure perfection
Celtic
Squad number15Player nameHart
Squad number56Player nameRalston
Squad number20Player nameCarter-Vickers
Squad number4Player nameStarfelt
Squad number88Player nameJuranovic
Squad number18Player nameRogic
Squad number16Player nameMcCarthy
Squad number14Player nameTurnbull
Squad number11Player nameAbada
Squad number10Player nameAjeti
Squad number17Player nameJota
Squad number12Player nameSoro
Squad number54Player nameMontgomery
Dundee United
Squad number1Player nameSiegrist
Squad number22Player nameFreeman
Squad number28Player nameSmith
Squad number12Player nameEdwards
Squad number33Player nameMcMann
Squad number23Player nameHarkes
Squad number8Player namePawlett
Squad number66Player nameFuchs
Squad number19Player nameLevitt
Squad number10Player nameClark
Squad number7Player nameNiskanen
Squad number3Player nameSpörle
Squad number27Player nameAppéré
Line-ups
Celtic
Formation 4-3-3
15Hart
56Ralston20Carter-Vickers4Starfelt88Juranovic
18Rogic16McCarthy14Turnbull
11Abada10Ajeti17Neves Filipe
15Hart56Ralston20Carter-Vickers4Starfelt88JuranovicSubstituted forMontgomeryat 26'minutes18Rogic16McCarthySubstituted forSoroat 45'minutes14Turnbull11Abada10Ajeti17Neves FilipeSubstitutes
5Scales6Bitton12Soro29Bain54Montgomery57Welsh73MoffatDundee Utd
Formation 4-3-3
1Siegrist
22Freeman28Smith12Edwards33McMann
23Harkes8Pawlett66Fuchs
19Levitt10Clark7Niskanen
1Siegrist22FreemanBooked at 90mins28Smith12Edwards33McMann23Harkes8PawlettSubstituted forAppéréat 79'minutes66FuchsBooked at 15mins19Levitt10Clark7NiskanenSubstituted forSpörleat 62'minutesSubstitutes
3Spörle6Reynolds11Chalmers14Hoti16Carson26Mochrie27AppéréLive Text
Match ends, Celtic 1, Dundee United 1.
Second Half ends, Celtic 1, Dundee United 1.
Attempt saved. Jota (Celtic) right footed shot from outside the box is saved in the top left corner. Assisted by Adam Montgomery.
Jota (Celtic) hits the bar with a right footed shot from outside the box.
Anthony Ralston (Celtic) wins a free kick in the defensive half.
Foul by Dylan Levitt (Dundee United).
Attempt saved. Louis Appéré (Dundee United) right footed shot from the left side of the box is saved in the centre of the goal. Assisted by Adrián Spörle.
Corner, Celtic. Conceded by Adrián Spörle.
Kieran Freeman (Dundee United) is shown the yellow card.
Foul by Ismaila Soro (Celtic).
Louis Appéré (Dundee United) wins a free kick in the defensive half.
Attempt missed. Carl Starfelt (Celtic) header from the centre of the box misses to the left. Assisted by David Turnbull with a cross following a corner.
Corner, Celtic. Conceded by Adrián Spörle.
Tomas Rogic (Celtic) hits the bar with a header from the centre of the box. Assisted by Jota with a headed pass.
Jota (Celtic) wins a free kick on the left wing.
Foul by Kieran Freeman (Dundee United).
Attempt missed. Jota (Celtic) right footed shot from the centre of the box is too high. Assisted by Tomas Rogic.
Attempt saved. Adrián Spörle (Dundee United) right footed shot from outside the box is saved in the top centre of the goal. Assisted by Dylan Levitt.
Substitution, Dundee United. Louis Appéré replaces Peter Pawlett.
Attempt missed. Albian Ajeti (Celtic) header from the centre of the box misses to the left. Assisted by Liel Abada with a cross.
