Nearly half of people who had Covid-19 feel only partially recovered between six and 18 months after being infected.
A study into the long-term effects on patients in Scotland found those who were older, female or from deprived communities were more likely to be affected.
Researchers at the University of Glasgow said symptoms of long Covid include chest pain, confusion and breathlessness.
Dr Jill Pell, who carried out the study, said she wants to see more support for those affected.
"Long Covid needs to be treated as a long term condition, it's certainly not the only long term condition in society, but it does need to be recognised that it can have long term impacts.
"People need to be supported with this condition as much as they are supported with other long term conditions," she added.
On Wednesday, The Guardian reported that long Covid is "devastating" the lives of millions, according to the head of the World Health Organisation (WHO).
Dr Tedros Adhanom Ghebreyesus urged countries to make efforts to tackle the "very serious" condition, which is affecting economies and health systems worldwide.
In September, TD Denis Naughton told the Dáil that 21,000 people cannot work because of long Covid symptoms, urging the Government to "act now".
"Based on my analysis of the social welfare payments for Covid-related illnesses, lasting 12 weeks or more following the initial infection, we’re looking at some 21,000 people in Ireland who are unable to go to work due to long Covid," Mr Naughten said.
"This figure does not take into account the tens of thousands who are suffering with less severe forms of long Covid, who are going to work but not contributing to the same extent that they did prior to the illness, nor does it take into account the thousands of people who recover from the initial infection but had a subsequent relapse."
He warned long Covid could lead to "very significant future burden of disease", adding: "We need to act now and we need to act in a comprehensive way."
