The Silver Line helpline for lonely and isolated older people has received its one millionth call in just over two-and-a-half years.
The charity's founder Dame Esther Rantzen, who launched the 24-hour phoneline number 0800 4 70 80 90 in November 2013, said that to have answered so many calls in such a short space of time is "desperately sad".
The millionth call came on a Sunday this summer when the free helpline was dealing with a record 1,600 calls, easily outstripping the surge of calls it got on New Year's Day 2016.
The Silver Line now needs to raise £1.65 million to pay for the night-time and weekends service, amid fears the service may have to be shut down with more public donations. Over two-thirds of calls to the helpline are at night and weekends and over half of all callers say they have no one else to speak to.
Dame Esther said: "Calls to the helpline increase almost every week as we uncover the epidemic of loneliness among our oldest and most vulnerable people.
"Our callers tell us that nights can be the worst times of all when they really need someone to talk to and confide in.
"We urgently need more donations to keep the night-time service going so we are always there for the people who need us most."
Silver Line's chief executive Sophie Andrews said: "Every day we speak to lonely older people who have led varied and interesting lives but are now isolated and literally have no one to speak to for days on end.
"Over 90% of our callers say they live alone and rely on the helpline - especially at night when other services are closed.
"We're the only helpline specifically for older people, which is there 24/7, every day of the week, including Christmas and Bank Holidays."
Anyone who wants to donate can go online - at www.thesilverline.org.uk/donate - to help.