The Steam Packet Company says the Manxman should arrive in Heysham shortly after midday following an incident earlier.
This morning, the vessel set off from Douglas bound for Lancashire shortly after 8am.
However, a medical emergency meant she had to return to the Island, where she was met by ambulance staff who took the patient to Noble's Hospital for treatment.
No details about their condition have been released.
The company says she set off again at 8.44am, and should arrive in the UK shortly after 12pm.
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