Hall faces a spell on the sidelines with an ankle injury, ruling him out of the Wembley showdown with Liverpool on March 16.
Magpies boss Eddie Howe was braced for the worst after Hall missed Sunday's FA Cup defeat at home to Brighton.
That is after picking up an ankle injury in the 2-0 defeat to Liverpool last week.
Those fears have now been confirmed after seeking specialist advice.
While it's unclear just how long he'll be ruled out for, the Wembley clash in under two weeks' time will come too soon.
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Speaking after the Brighton game, Eddie Howe said: "We're waiting to see.
"It is an ankle problem that Lewis Hall picked up after the Liverpool game and had some pain towards the end of the game.
"He didn't really recover well, he has a bit of swelling there.
"So he had a scan and now he has been to see a specialist. We are awaiting further news."
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As a result it means that Newcastle could be without their first-choice left-side pairing.
Newcastle are already without Anthony Gordon due to suspension as they bid to end their trophy drought.
The winger picked up a red card after losing his head during the 2-1 defeat to the Seagulls at the weekend.
While it had been suggested that the Magpies could look to appeal the ban, the club have decided not to which means that a three-match ban will stand.
As a result he'll miss the trip to West Ham, the Carabao Cup final and the home clash with Brentford on April 2.
Hall and Gordon were set to be tasked with keeping Liverpool's dangerous right-flank quiet at Wembley.
Trent Alexander-Arnold and Mohamed Salah have been prolific down the flank.
With Newcastle's first-choice pairing now sidelined, it means that Eddie Howe will have to come with an alternate plan.
Hall was also expected to be named in Thomas Tuchel's first England squad for the international fixtures this month.
The Three Lions will take on Albania and Latvia with the Newcastle star expected to play at left-back, however his latest injury blow could end his hopes of featuring.
Hall has been a key player for Newcastle this term.
In 34 appearances for the club, he has contributed to