Salwonir Joskowski, 34, was taken to St Mary’s Hospital in the early hours of Sunday (April 9) after he was found collapsed in the street.
But he left the hospital before his treatment had concluded and there are therefore ongoing concerns for his health.
Mr Joskowski, who is believed to be from Dartford, is described as white, of medium build with cropped hair.
When last seen he was wearing a white Superdry hooded top and jeans, and was carrying a bag.
Anyone who has seen Mr Joskowski is asked to contact officers at Westminster via 101.