It has been described as an ''invisible epidemic'' which some believe is as harmful to health as smoking.
Across Wales, a survey found nearly half a million people are living with loneliness.
For Vic Brown, it took hold of his life very suddenly after the death of his wife from sepsis. They had been together for more than forty years.
''Loneliness is almost like an emptiness,'' he said.
''I'd never felt it in my life but when you've lost the person who was more or less your right arm it's like an emptiness I can't explain.
You despair because you've got nobody to talk to, nothing to do and you've got nothing to focus your life on.''
Research has found loneliness can have a profound physical effect on the body, with those suffering more likely to have high blood pressure and heart disease.
It can put an extra strain on services too. Dr Deborah Morgan from Swansea University says there is evidence people who are lonely will visit GPs just to find someone to talk to.
Loneliness is something that can touch people of all ages.
In Llandrindod Wells, a group of new mums meet regularly at a support group where they can talk openly. Loneliness is a common theme.
For Laura Watkins, being a new mum has sometimes been a lonely experience.
''It takes your breath away because you are really happy that you have this tiny person,'' she said.
I don't think anyone else can really experience that night time loneliness. That loneliness where the responsibility of your baby is ultimately yours.''
Vic has found a solution to his loneliness in the form of a social group called Men's Sheds.
He meets with his new friends to take take part in DIY projects. Working with the other members has helped him cope with the loss of his wife.
''Men don't normally talk to each other like women,'' he said.
They talk to each other shoulder to shoulder. When you're doing something you can chat about things, like loneliness.''
Joining the group has been Vic's way of combating loneliness. Speaking out is often the first step.
You can see more on Wales This Week: When Lonely Comes to Call, Thursday 14th February at 8:30pm on ITV Cymru Wales.