In short: An ADHD assessment is a structured clinical evaluation, usually lasting 1.5 to 3 hours, carried out by a specialist such as a psychiatrist or an appropriately trained clinician. It looks at your current symptoms, how they affect your daily life, and whether they were present in childhood. A diagnosis is only made if you meet recognised criteria (DSM-5 or ICD-11) and your symptoms cause meaningful difficulties in more than one area of life.

This guide, written by a Ready Health prescribing pharmacist, explains each stage of an ADHD assessment for adults and children, how to prepare, and what happens afterwards.

What is ADHD?

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition. It affects attention, activity levels and impulse control. Symptoms begin in childhood, although many people are not recognised until adulthood, particularly women and people whose difficulties show up mainly as inattention rather than hyperactivity.

Common features include:

Difficulty sustaining focus, finishing tasks or organising time
Frequently losing things or forgetting appointments
Restlessness, fidgeting or feeling "on the go"
Acting or speaking without thinking, interrupting others
Emotional ups and downs and difficulty managing frustration

Many of these experiences are common in everyone at times. ADHD is considered when they are persistent, started early in life and cause real problems at home, work, school or in relationships. Read more about ADHD symptoms in women.

Who can diagnose ADHD in the UK?

NICE guideline NG87 says ADHD should only be diagnosed by a specialist psychiatrist, paediatrician or other appropriately qualified healthcare professional with training and expertise in diagnosing ADHD. GPs, teachers and online questionnaires cannot make a diagnosis, although they can play an important part in recognising symptoms and supporting a referral.

What happens in an ADHD assessment?

Assessments vary slightly between services, but most follow a similar pattern.

1. Pre-assessment questionnaires

You will usually be asked to complete validated rating scales before your appointment. Adults often complete screening tools about current and childhood symptoms. Where possible, someone who knew you as a child (for example a parent or older sibling) or who knows you well now (such as a partner) may be asked to complete a questionnaire too. For children, parents and teachers are normally asked for information.

2. The clinical interview

This is the main part of the assessment. The clinician will ask about:

Your current difficulties and how long you have had them
Your childhood, schooling and any reports or comments from teachers
Work, study, relationships, driving and money management
Physical health, sleep, alcohol and drug use
Mental health history, including anxiety, depression or trauma
Family history of ADHD or other neurodevelopmental conditions

A structured diagnostic interview, such as the DIVA-5 for adults, is often used so that each symptom is explored in a consistent way.

3. Looking at other explanations

Several conditions can look like ADHD or occur alongside it, including anxiety, depression, autism, sleep disorders, thyroid problems and substance misuse. A good assessment considers these carefully so that the conclusion is accurate.

4. Outcome and report

The clinician explains whether you meet the criteria for ADHD and why. You should receive a written report summarising the findings and recommendations. If ADHD is not diagnosed, the report may suggest other support or assessments.

How long does an ADHD assessment take?

The appointment itself commonly lasts between one and a half and three hours, sometimes split across more than one session. Allow extra time for questionnaires beforehand and for the report to be written afterwards. Assessments may be in person or by secure video call, depending on the service and what is clinically appropriate.

How can I prepare for an ADHD assessment?

Gather old school reports if you can find them
Ask a parent, sibling or partner whether they are willing to share information
Write down examples of how symptoms affect you day to day
Bring a list of current medicines and any relevant medical letters
Note any questions you want to ask

What happens after an ADHD diagnosis?

NICE recommends that treatment planning starts with information, support and practical strategies. For some people, medicine may also be considered. ADHD medicines are prescription-only and are started by a specialist after checks such as blood pressure, heart rate, weight and a review of your medical history. A prescriber decides whether any medicine is suitable for you, and some people choose not to take medicine at all.

If you were diagnosed privately and want your GP to continue prescribing, this depends on a shared care agreement. GPs are not obliged to accept shared care, so it is worth discussing this before you start treatment.

Can I have an ADHD assessment privately or through Right to Choose?

Yes. You can ask your GP for an NHS referral. In England, if your GP agrees a referral is appropriate, you may be able to use your legal Right to Choose to select an NHS-contracted provider. Private assessments are also available and can offer more flexibility over appointment times. Whichever route you choose, check that the clinician is suitably qualified and that the assessment follows NICE guidance.

Frequently asked questions

Can I be assessed for ADHD as an adult?

Yes. Many people are first diagnosed in adulthood. The assessment will still ask about childhood, because symptoms need to have started early in life.

Do I need a GP referral for an ADHD assessment?

For an NHS assessment, usually yes. Private services may accept self-referral, but it helps to share your medical history with the assessing clinician.

Can an online test diagnose ADHD?

No. Online questionnaires can help you decide whether to seek an assessment, but only a qualified clinician can diagnose ADHD.

Will I definitely be offered medication?

No. Treatment is a shared decision. Medicine is only prescribed if a specialist judges it suitable and you agree.

What if I am not diagnosed with ADHD?

The clinician should explain the findings and may suggest other causes for your difficulties and where to get support.

Key takeaways

ADHD can only be diagnosed by a suitably qualified specialist following NICE guidance.
Assessments combine questionnaires, a detailed interview and information from people who know you.
Symptoms must have started in childhood and affect more than one area of life.
Other conditions are considered so the diagnosis is accurate.
Treatment options include support, practical strategies and, where appropriate, medicine decided by a prescriber.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

If you are in Wigan, Standish or the surrounding area and would like to talk through your symptoms, find out more about our ADHD assessment and diagnosis service or our online ADHD assessment.

What Happens in an ADHD Assessment? A Step-by-Step Guide