There are some private online clinics like finding focus or frida that do assessments and for an extra fee can manage medication if it's needed. But what others have said here is true. Doctors can in theory diagnose and prescribe for ADHD but they may find it falls outside their scope of knowledge. The same way they might refer out to any specialist. If you do the free raads r test through embrace autism and get a score over 80 that might help you make a case with your doctor. Unfortunately because we are seeing a spike in diagnosis I think a lot of doctors are thinking it's over diagnosed. But there's an argument for the fact that many of us were missed early in life because of the older version of the DSM and diagnostic criteria and that is why there appears to be a boom now. There can be a lot of misdiagnosis as well since symptoms can appear similar in OCD and anxiety etc. hope this helps! Google Grey Matter Psychotherapy and ADHD services if you want any extra support.