Whilst I generally try to avoid medical language to describe the Autistic experience, I use the word diagnosis here to describe the process of being formally identified as autistic by a healthcare professional, usually a psychologist or psychiatrist.
If you are exploring whether you might be Autistic as an adult, it is a personal choice whether you decide to self-identify as Autistic after carrying out your own research and meeting other Autistics, or whether you feel you need a formal diagnosis, perhaps in order to get reasonable adjustments at work or get friends or family to accept that you are Autistic. Or you may feel unable to identify as Autistic without a formal diagnosis, even if others believe you.
A formal diagnosis is not accessible to all Autistic people, sometimes there are no free services and the cost of getting a private diagnosis is too much, sometimes there is a lack of up-to-date knowledge of Autism in the person carrying out the assessment and the diagnostic criteria is too narrow. Sometimes prejudice against women, non-binary people, trans people or people of colour will be a barrier to getting a formal diagnosis.
For this reason self-identification is accepted as valid within the Autistic community, and most groups will accept Autistics who are self-identified.
If you do wish to pursue a formal diagnosis, the following services may be of help. These are not recommendations as I have not used them personally but they are examples of what is available.
As many people are both Autistic and ADHD (AuDHD), it would be worth considering whether you would like an autism assessment or a combined autism and ADHD assessment.
Identification and Diagnosis (General)
Neuroclastic’s community-generated Directory of Specialists Diagnosing Autism in Adults (Global directory)
The Adult Autism & ADHD Practice – Private Autism & ADHD Assessments | Collaborative Autistic/ADHD Identification for Adults in the UK, Ireland and (almost) Worldwide Online