A quarter of adults diagnosed with asthma in the UK may not actually suffer from it, according to an NHS watchdog.
The inflammatory respiratory disease affects people of all ages, and causes such problems as wheezing and attacks of breathlessness.
There is no definitive test to identify the disease, however, which means doctors have to base their diagnoses on experience and symptoms rather than clinical evidence.
According to the National Institute for Health and Care Excellence (Nice), this means that over one million of the 4.3m UK adults who have been told they suffer from asthma, over a million may have been inaccurately diagnosed.
The public health body says that since these individuals show no clinical symptoms of the disease, they may in fact be suffering from other disorders which have similar impacts on the respiratory system.
Since asthma treatments can have some negative side effects, Nice has urged people who think they might have been inaccurately diagnosed to go and see their doctors. However, they advise no one to stop taking their treatments of their own accord.
Additionally, unrequited treatment could be costing the government vast sums of money – each year, the NHS spends an estimated £1bn on treating and caring for the country's asthma sufferers.
To improve the accuracy of diagnosis, Nice has proposed some new guidelines for doctors to adhere to when dealing with a potential asthma case, and hopes they will have come into effect by the summer.
Rather than using their own experience, they are encouraging the adoption of more clinical tests, such as the use of spirometry – a machine allowing doctors to measure how much and how fast a person breathes out.
Prof Mark Baker, director of clinical practice at NICE, told the BBC: "Accurate diagnosis of asthma has been a significant problem which means that people may be wrongly diagnosed or cases might be missed in others.
"Our aim with this guideline is to give clarity and set out the most clinical and cost-effective ways to diagnose and monitor asthma based on the best available evidence."