The 34-year-old, who came through the academy at the club, returned to Anfield in the summer in a player-coach role.
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Along with being a coach for the Under-18s, the 2012 League Cup winner was registered as an over-age player for the Under-21 side.
He was even a replacement for Brazilian star Arthur earlier in the season during a Papa John's Trophy clash against Rochdale.
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But in a shock for Spearing, he has declared how he has been diagnosed with a rare disorder of the adrenal glands.
In an honest Instagram post, the ex-Bolton midfielder said: "My First Christmas off in 17 years was a little different than I expected.
"After blood tests with the club, on Xmas Eve I was told I needed to attend hospital urgently before my body starting shutting down.
"I was potentially hours/days away from going into something called Adrenal Crisis.
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"After more observations and tests… they diagnosed me with Addison's Disease.
"It's took me a minute to get my head around it, but I am thankful that now it's been diagnosed it can be controlled and managed through hormone replacement treatment, and it's not something that I will allow to effect or dictate my life."
Before adding: "Don't ignore changes in your body… no matter how small… get them checked out."
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There are around 300 new cases of Addison's Disease each year in the UK, which is a rare, lifelong condition.
The disorder can lead to darkened skin as a result of the adrenal glands - which are located on top of your kidneys - not producing enough hormones.
Though it can be life-threatening, it can be treated successfully with steroid hormones.
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A number of Spearing's former teammates were quick to show their support, with Liverpool skipper Jordan Henderson posting a love heart emoji.
Stefan Bajcetic, who scored for Liverpool against Aston Villa on Boxing Day, said: "Get well soon Jay."
Meanwhile ex-Reds left-back Jose Enrique messaged: "Glad you are OK amigo. Much love."
Arsenal defender Rob Holding messaged: "Get well soon mate."
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His ex-Trotters teammate Stuart Holden remarked: "Thinking of ya fella, glad you caught it early!
"Rest up and get your a*** back out on the pitch!!! Merry Christmas man hope to see you soon."