East London NHS Foundation Trust has connected 50 of its sites to a fibre optic network from Virgin Media Business.
The trust said it had "dramatically boosted reliability" and speeds for desktop users accessing applications "fivefold". Its average network speed is 10 Megabits-per-second (Mbps).
East London, which provides mental health and community health care to people within the City of London and the London Boroughs of Hackney, Tower Hamlets and Newham, said the fast connectivity was vital as its 3,700 employees access critical applications.
Systems being accessed across the network include patient records services, internal clinical systems and some NHS national applications such as booking systems.
The system replaces an ATM-based network that often experienced long outages.
Jonathan Buchan, IT Manager at the trust, said: "The NHS uses a lot of hosted applications. We looked at various alternatives but found that ADSL-based solutions are just not as reliable or as fast as the fibre optic solution that Virgin Media Business is providing us with."
"Additionally, the Ethernet VPN offering is the only product on the market that we can use straight away without customising it or investing our time implementing."