Alistair McDonald, 46, from Bracknell, was seen leaving the Reading hospital at about 11.30pm where he was receiving medical treatment.
He is white, 5ft 10ins tall and clean-shaven with dark brown hair and was wearing a black shirt and black three-quarter length trousers.
Investigating officer Inspector Carl Borges said: “We are becoming increasingly concerned about Mr McDonald’s welfare.
“We are unsure whether Mr McDonald has access to any funds and do not believe he has the medication he requires with him and may require further medical treatment.”
Anyone with information should contact Thames Valley Police on 101 and ask to speak to the Reading duty sergeant.
Anyone who does not wish to speak to the police directly, can contact Crimestoppers anonymously with information on 0800 555111.