A hospital trust is warning its patients to leave extra time for their journeys on July 7 when the Tour de France passes through Waltham Forest.
The world's most famous cycle race will pass through Epping, Redbridge and Waltham Forest during stage three of the race from Cambridge to London.
Main routes leading towards Whipps Cross Hospital such as Woodford New Road and Lea Bridge Road will be closed from 10am until 6pm as up to 220 cyclists are expected to pass through at around 2.30pm.
Whipps Cross Hospital director Jonathan Lofthouse said: "This is a hugely exciting event for London, but it will inevitably mean some delays in getting to and from our hospital that day.
"All hospital appointments will be going ahead as planned, but we’re asking patients and anyone else visiting the affected sites to allow plenty of time for their journey so that they get to us in good time.
"We’d urge everyone to plan ahead and do whatever is necessary to ensure they do not miss their appointment."
Many bus routes will be diverted and some stops will be temporarily relocated or suspended for several hours.
Spectators are expected to line the streets at key viewing points such as Whipps Cross Roundabout, Leyton Green and Lea Bridge Road.
Waltham Forest council is to set up a big screen at Whipps Cross Roundabout and has organised a family fun day at Leyton Jubilee Park in Seymour Road on June 6.
The British and French themed event will include sporting activities such as cycling, paralympic cycling, boules and polo as well as a zip wire, gyroscopes, pedal karts and a climbing wall.
For further information, see the TfL website, which carries full details of expected travel disruption and advice. Go to: http://www.tfl.gov.uk/campaign/tour-de-france-2014.