The Blues had been investigating the circumstances surrounding Hollands' concerning and erratic performance at the MCG on Thursday night.
On Monday night, Carlton released a statement confirming Hollands was in hospital.
"The Carlton Football Club can confirm that Elijah Hollands has been admitted to hospital this evening," the Blues said in a statement.
"While the club acknowledges the public's interest, it again asks that the privacy of Elijah and his family be respected.
"This request for privacy extends to the media to please not report or speculate on Hollands' location and private health information."
Hollands had been getting support from his father Ben, and Carlton had already ruled him out of travelling to Perth for Saturday night's match against Fremantle, in the wake of what it said was his "mental health episode" against the Magpies.
The 23-year-old Hollands initially ended Thursday night's defeat at the MCG without registering a statistic, despite playing 75 per cent of the match across the first three quarters, and was benched during the fourth term.
He was eventually awarded a possession by Champion Data in retrospect, an ineffective kick in the third term.
Several videos circulated online after the match appearing to show Hollands confused and exhibiting erratic behaviour on the field.
The AFL has asked Carlton for a review of the circumstances around what happened with Hollands to be provided to the league once it has been completed.
On Sunday, Carlton chief executive Graham Wright was unable to explain why Hollands returned to the field in the last quarter. Nor could he explain when personnel from Carlton's football department realised he was struggling.
Last year, Hollands twice took personal leave from Carlton, later revealing he had been battling mental ill-health and issues with alcohol.
On Sunday, Wright said he "at this stage" ruled out alcohol or illicit substances being factors affecting Hollands during the match.
"We're dealing with a mental health issue ... right at the moment," Wright told reporters.
"We're in the process of going through all the circumstances leading up to the game, two or three weeks prior to the game.
"Our primary focus remains on caring for Elijah, making sure he continues to receive the medical and well-being support he needs.
"Elijah's mental challenges have been well documented.
"Our staff have been working alongside Elijah on this journey with him over a long period of time now, both on and off the field, providing every resource possible to ensure his welfare is paramount.
"Thursday night presented unprecedented and complex circumstances. We're taking this very seriously."
Hollands, who turns 24 on Saturday, was delisted by the Blues at the end of last season, despite having a year to run on his contract.
But he was invited to Carlton training over summer, and impressed enough to win his spot back on the list.
He has played all six games this season, averaging 18.4 possessions before his concerning night against the Magpies.
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