Hi Repsol, Im not a medical personnel... so this is based only on my experience and research. If you are talking about the technical aspect of diagnostic process, then the waiting time depends on the procedure employed. For example, Doctors could promptly give readings on Scan results as soon as they have the scan to read. Meanwhile some laboratory procedures (like those that involves growing cellular cultures) could take weeks or months to have a results. If you are talking about the administrative aspect of diagnosis, then that depends from country to country, even hospitals to hospitals. Im not from UK so couldnt answer how UK medical service works. In my country there is a significant difference between a public run hospital and a private run hospital. Public hospitals, usually, dont readily recommend expensive diagnostic procedures like X-ray or CT-Scan, unless truly necessary or in a case of emergency. So public doctors usually try to make initial diagnosis based only on patient interviews, suggest treatments based on that, and will rather wait for further development. Of course, if the disease is much more serious then it could take a significant amount of time to have a proper diagnosis which would in turn delay the administration of a proper treatment. Private hospitals however, will also try to make initial diagnosis and treatments based on patient interviews (to arrest any immediate suspicion of infections, for example) but they will also recommend more complicated diagnostic procedures (such as scans, lab tests etc) running in parallel to the initial treatment to capture all possible causes of the ailments. Of course some could argue that private hospitals do that just to make a lot more money by recommending "unnecessary" and expensive diagnostic procedures.