The centrepiece of the scheme is the 'Boiler Suit' (pictured) - a facade surrounding the boiler that powers the hospital, formed of 108 tiles made of woven stainless-steel braid.
The scheme - Heatherwick's first commission for the NHS - also includes widened pavements, a one-way traffic system with designated drop-off points, new signage, CCTV, lighting and a shop.
The project has been funded by the Pool of London Partnership, Guy's and St Thomas' Charity and the Friends of Guy's Hospital.
Karen Sarkissian, director of art and heritage at Guy's and St Thomas' Charity, said: 'It has been enormously rewarding and exciting to commission such a prestigious designer to work with us.
'Thomas has come up with an eye-catching design which you would not expect to encounter on a hospital site.'