The Blues were defeated at home, despite a second-half header from Jon Mellish.
Sam Smith broke the deadlock after latching onto a lofted through ball by Lewis Wing, before Harvey Knibbs doubled their lead on 36 minutes after an outstanding run from the Royals’ right-back Andy Yiadom.
Knibbs bagged his second and Reading’s third from close range on 57 minutes following a Femi Azeez cross.
Prior to Jon Mellish pulling a goal back for United after powering a header beyond David Button.
Luke Armstrong had two huge opportunities to break the deadlock in the opening few minutes following a well-worked free-kick between Taylor Charters and Jon Mellish, with the latter finding our striker in the middle, but he was unable to turn home at the near post on both occasions.
United continued their early pressure with Jack Diamond looking to find Armstrong on 13 minutes, but Reading cleared the danger.
The Royals came agonisingly close to finding the first goal of the contest on 15 minutes. Harrison Neal was robbed on halfway before attacker Sam Smith went through one-on-one with Harry Lewis, but he struck the post.
Two minutes later they found the breakthrough, and it was Sam Smith who got it. Lewis Wing chipped a ball over United’s defence into the path of the attacker and this time he made no mistake, knocking the ball into the far corner to put the visitors ahead.
On 25 minutes, Femi Azeez picked out Harvey Knibbs from a corner, but the midfielder’s headed effort flew over.
Moments later, Harry Lewis made a strong low save following a mistake whilst passing out from the back.
Diamond provided the next big chance of the game as he drove forward into the area before lashing an attempt on goal, which ultimately went over the bar.
The visitors extended their advantage on 36 minutes, an exceptional run from Reading skipper Andy Yiadom down the right ended in him finding Knibbs in the centre of the box, who tapped in the Royals’ second.
Amadou Mbengue defended brilliantly as we approached half-time, denying both Mellish and Armstrong who looked to be through on goal.
Two minutes before the break, Lewis Wing took aim from distance, but Harry Lewis managed to claim.
The final action of the half drew Harry Lewis into a tremendous low save at full stretch, following Azeez’s left-footed effort.
Half-time: Carlisle United 0-2 Reading
The second-half started with the hosts applying pressure, but Reading continued to defend brilliantly.
On 52 minutes, Taylor Charters delivered a free-kick which was met by Mellish, but his nodded effort went over David Button’s crossbar.
One minute later, the Royals had a shout for a penalty waved away as Jack Armer battled with Azeez - the referee deeming the coming together as legal.
Lewis was forced into tipping Azeez’s shot over the bar on 57 minutes, following a long throw into United’s area.
Seconds later Reading had a third, Azeez’s cross fell to the feet of Knibbs, who bundled home to double his tally.
Following the goal, Jordan Gibson and Alfie McCalmont were introduced and they combined to try and pull a goal back on 61 minutes, but after fine build-up play between the pair, nobody was free in the box to fire at Button’s goal.
Kelvin Ehibhationham looked to add a fourth shortly after, but Lewis turned behind for a corner.
On 64 minutes, the Blues looked to break down the left, Armer’s delivery found Armstrong but his strike was straight at the ‘keeper.
It was those two who linked up again moments later, but once again it ended in nothing for Carlisle.
Paul Simpson’s men continued to fight despite being three down and Neal created a brilliant chance on 68 minutes. The midfielder played a reverse ball into the path of Mellish, but the latter was unable to square the ball to a teammate.
On 71 minutes, Gibson whipped a terrific free-kick into the area, and Mellish thundered his header beyond Button to make it 3-1.
Sam Smith looked to bag his second as we approached the final ten minutes, but he headed wide of United’s goal.
On 81 minutes, Gibson hammered an effort from distance, but it flew just wide of the Royals’ goal.
As we entered the closing stages, newly-introduced Dan Butterworth swung at the ball at the far post, but Button was equal to it.
Full-time: Carlisle United 1-3 Reading
Goals
Carlisle United: (Mellish 71’)
Reading: (Smith 17’), (Knibbs 36’ 57’)
Bookings
Carlisle United: N/A
Reading: N/A
Teams
Carlisle United: Lewis, Armer, Lavelle, Huntington ©, Charters (Gibson 59’), Ellis, Mellish, Diamond (Butterworth 79’), Neal, Armstrong, Vela (McCalmont 59’)
Unused subs: Breeze, Robinson, Maguire, Grehan
Reading: Button, Mola, Knibbs, Smith, Azeez (Abrefa 89’), Ehibhationham (Elliott 66’), Yiadom, Bindon, Mbengue, Wing, Craig
Unused subs: Pereira, Dean, Savage, Mukairu, Wareham
Match Officials
Referee: Martin Coy
Assistant Referee 1: Bradley Hall
Assistant Referee 2: Paul Newhouse
Fourth Official: Simon Clayton
Attendance: 7891 (1360 away)