The new service goes a step further by enabling an instant chat session that experts say can make all the difference with someone seeking help.
"The science shows that people experience reductions in suicidal thinking when there is quick intervention," said Lidia Bernik, associate project director of Lifeline. "We've heard from many people who say they want to talk to someone but don't want to call. Instant message is perfect for that."
How the service works is if a friend spots a suicidal thought on someone's page, he can report it to Facebook by clicking a link next to the comment. Facebook then sends an email to the person who posted the suicidal comment encouraging them to call the hotline or click on a link to begin a confidential chat.
Facebook on its own doesn't troll the site for suicidal expressions, Wolens said. Logistically it would be far too difficult with so many users and so many comments that could be misinterpreted by a computer algorithm.
"The only people who will have a really good idea of what's going on is your friends so we're encouraging them to speak up and giving them an easy and quick way to get help," Wolens said.
There have been high profile incidents of suicidal expressions on Facebook.
Last month, authorities in Pittsburg said a man posted a suicide note on Facebook before he killed his wife and in-laws then himself.
In July, police in Pennsylvania said they believed they were able to help prevent a man's suicide after the man's friend in California alerted police about a distraught Facebook posting. Police met with the man, who was committed to a hospital.
Nearly 100 Americans die by suicide every day, and 36,035 a year, according to U.S Surgeon General Regina Benjamin's office.
"We have effective treatments to help suicidal individuals regain hope and a desire to live and we know how powerful personal connections and support can be," Benjamin said in a statement. "Facebook and the Lifeline are to be commended for addressing one of this nation's most tragic public health problems."