The race is the first major marathon since Monday's Boston Marathon where three people were killed and more than 170 injured by two explosions near the finish line just after the race's 4-hour mark.
Officials have termed the explosions an act of terrorism.
Race organizers in London said Tuesday that ceremonies at the start of their race will include a 30-second period of silence in memory of the victim of the attack in Boston. London runners will be given a black ribbon to wear.
There will also be increased security for the 35,000 runners and an expected 500,000 spectators lining the 26-mile, 385-yard course
"You look at what has occurred, if there are steps we can take to increase security and all sorts of measures one could deploy," London Marathon Chief Executive Officer Nick Bitel told BBC Radio 5 Live.
"We run through the city. When you have an event of any nature, a marathon, parade, it's only as safe as the city itself. If it's not held in a stadium, you can't do a lockdown like you may do in a building."
Metropolitan Police Commissioner Bernard Hogan-Howe told the BBC that security personnel were going over their existing plans.
"We've no reason to think [runners and spectators] are any less safe than they were before the terrible events in Boston," he said.
Hogan-Howe said officers will increase searches and increase the numbers of officers on the streets for the race.