Autism Diagnosis: Process, Criteria, Cost and Next Steps

• OVERVIEW
• SYMPTOMS
• ADULTS
• CHILDREN
• WOMEN
• DIAGNOSIS
• TREATMENT
• MEDICATION

When you’re thinking about an autism diagnosis, a lot of questions come up. What exactly is autism? What signs or symptoms should you observe? What will a diagnosis cost in the UK? Whether you’re seeking answers for yourself, another adult or your child, getting a clear understanding of autism is necessary to reduce uncertainty and help you decide what to do next.

This guide offers a clear explanation of how autism is diagnosed, what an assessment involves, who conducts it, and how public and private diagnosis pathways differ. It draws on the clinical experience of AuDHD Psychiatry — a neurodivergent-informed practice specialising in adult and child autism assessments, following NICE-aligned diagnostic frameworks and producing reports that GPs routinely accept for shared care.

Key Takeaways

• An autism diagnosis follows a comprehensive and structured process in the UK, beginning with a referral from a GP to an autism specialist.
• An assessment is conducted according to autism diagnostic criteria, following the DSM-5 or ICD-11, with guidance from NICE.
• After an autism diagnosis, it’s important to give yourself or your loved one time to come to terms with the results and to recognise that adequate support is available to manage the challenges of the condition.

How Is Autism Diagnosed?

An autism diagnosis in the UK follows a comprehensive process. It starts with a referral from a general practitioner (GP) for an autism specialist. The specialist will perform an assessment in accordance with recognised autism diagnostic criteria. These are listed in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) or the International Classification of Diseases 11th Revision (ICD-11), following guidelines from the National Institute for Health and Care Excellence (NICE).

What happens during an autism assessment?

In addition to using the DSM 5 autism criteria or the ICD-11 criteria, the specialist will also use their clinical judgment in diagnosing autism. They will:

• Ask about the person’s medical history
• Ask about their family history
• Carry out direct observations
• Provide a skills assessment to identify strengths and challenges
• Use a range of diagnostic tools, such as the Autism Diagnostic Interview-Revised (ADI-R) and the Childhood Autism Rating Scale–Second Edition (CARS-2). 

The autism specialist will collect as much information as possible to determine whether a person has autism, what type of autism it is and what level of support they’ll need.

Some assessments may also take place over multiple appointments as the specialist observes the person at home, in school and across different settings.

How Long Does an Autism Diagnosis Take?

An autism diagnosis can take several months from the time you get a referral from your GP. In England, the waiting period for getting an assessment should be no longer than three months, according to NICE guidelines.

While the referral is processed, you may be asked to complete a screening questionnaire before your clinical appointment. Once you make that appointment, another waiting period follows while the diagnostic tests are evaluated. Another clinical appointment may be arranged for the specialist to conduct interviews with family members and friends who can share further information to create a detailed report.

How to Get Diagnosed for Autism

If you think you or someone you care about might be autistic, the most reliable next step is a clinician-led autism assessment. Neurodivergent-informed autism specialists focus on understanding how a person experiences the world rather than framing autism purely in terms of deficits. A thorough assessment can help clarify whether autism is present, and it can guide the appropriate next steps.

The UK follows a structured assessment process in diagnosing autism, but you have a few different pathways to choose from.

1. NHS Autism Assessment

Talk to your GP about the signs you’ve been exhibiting. If it’s your child, talk to your paediatrician or to the special educational needs co-ordinator (SENCO) staff at your child’s school. Get a referral for an autism assessment because this is an NHS requirement.

Once you receive a referral, you will be placed on a waiting list to see a specialist. Currently, waiting periods in the UK are 13 weeks.

2. Private Autism Diagnosis

Private autism assessment moves faster than the NHS route. A private autism diagnosis in the UK is carried out by chartered psychologists or psychiatrists. They follow prevailing clinical guidelines and NICE recommendations for autism in children or adults. 

The adult assessment includes a developmental history and validated tools with a detailed report of the findings and signposting for support. Child autism assessments include clinical interviews, with reports for school and home, plus practical recommendations.

3. NHS Right to Choose

Under this route, you can access NHS-funded services from approved providers, helping reduce waiting times.

How much does a private autism diagnosis in the UK cost? The cost varies, but it generally ranges from about GBP 1,000 to GBP 3,000. At AuDHD Psychiatry, we provide transparent pricing for autism assessments.

What Happens After an Autism Diagnosis?

An autism diagnosis can be overwhelming and emotional. Give yourself or your child time to understand the results or to be upset about them. Everyone reacts differently to a diagnosis, but reactions will change over time as you or someone you care about learns more about the condition and accesses autism support.

The formal support will depend on specific needs. According to NICE guidelines, autistic people should be allotted a key worker who will come up with a personalised plan following a diagnosis. 

The plan should cover:

• Needs for social, health, education and employment needs
• Action steps to address triggers of distressed behaviour
• Further support for co-occurring conditions like ADHD, such as an AuDHD assessment
• Additional support for the autistic person and their family

An autism spectrum disorder diagnosis will also require more than one specialist. Apart from a key worker, a primary healthcare worker, a speech and language therapist and other professional autism experts.

Frequently Asked Questions on Autism Diagnosis

Seek Clarity About Autism

An autism diagnosis involves a comprehensive clinical assessment. Often, it requires a multidisciplinary team including a GP, a chartered psychologist or psychiatrist, a nurse, a social worker, a speech and language therapist, and other healthcare professionals. The process can take place over several months if you’ve chosen the NHS assessment route or over a few weeks if you’ve chosen a private autism diagnosis.

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