At Oxo Tower Wharf the new colour-changing lighting system was put to good effect.
Elsewhere on the South Bank, the IBM Building and the National Theatre joined the initiative.
The London Eye is usually lit pink in recognition of its sponsor Lastminute.com but on Thursday night it was blue to match the NHS logo.
The Shard also took part, as did Tower Bridge.
The Illuminated River project to light up Thames bridges turned Cannon Street Railway Bridge and Southwark Bridge blue for the evening.
Both Guy's and St Thomas' NHS Foundation Trust and the London Ambulance Service – which is based in Waterloo – have thanked local people for their cheers and applause that rippled around the capital and the nation at 8pm on Thursday.