The 57-year-old was transported from Barwon prison in Geelong, in the state's southwest, about 8pm on Thursday after falling ill.
The Department of Justice and Community Safety confirmed a prisoner had been taken to hospital.
"One prisoner was taken to hospital last night by non-urgent ambulance," a spokeswoman said.
"Corrections Victoria does not comment on individual prisoners or their placements."
In 2019, the underworld figure sustained serious head injuries during a prison attack by two other inmates.
He spent more than three weeks in a coma after the attack and was left with cognitive issues impacting his memory, planning, organisation and reasoning skills.
He also suffered two heart attacks in March and April last year and later underwent stent surgery.
His barrister Julie Condon KC told Victoria's Court of Appeal in February Mokbel should be transferred to another prison and that his medical care had been "wanting".
Mokbel pleaded guilty to three counts of drug trafficking and was convicted and sentenced to 30 years in prison in 2012.
One of his convictions - importing a commercial quantity of cocaine from Mexico - was quashed by the appeal court in December 2020 after his former lawyer Nicola Gobbo was outed as a police informer.
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