Background: The long coronavirus disease 2019 (COVID-19) syndrome is defined as persistent physical, cognitive and/or psychological symptoms that continue for more than 12 weeks following the acute illness. Methods: In all, 2,646 patients were randomly selected from all individuals who were diagnosed with COVID-19. They were interviewed so as to assess the persistence of symptoms and health-related quality of life. Blood investigations were also taken. Results: The median (interquartile range (IQR)) age was 44 (31–55) years and 48.6% were males. Five per cent had been hospitalised. Follow-up was for a median of 142 days (IQR: 128–161). Twenty-two per cent of the participants claimed that they were feeling worse than they felt before COVID-19. The most common symptoms were anosmia, ageusia, fatigue, shortness of breath, headaches and myalgia. The Short Form-36 questionnaire revealed that 16.4% felt that they were somewhat worse than in the previous year and that hospitalised patients fared worse in all domains except for role-emotional. New-onset diabetes was similar to the rate of undiagnosed diabetes in the background population. Hospitalised patients had significantly higher liver transaminases, fasting plasma glucose, glycated haemoglobin, uric acid, red cell distribution width, mean platelet volume, triglyceride levels and troponin levels but lower estimated glomerular filtration rate and high-density lipoprotein-cholesterol at follow-up. Discussion: A significant proportion of patients were symptomatic at a median follow-up of 142 days and felt worse than 1 year previously. Hospitalised patients had more biochemical and haematological abnormalities compared to non-hospitalised ones, suggesting ongoing inflammation in subjects who were more severely affected by the disease.