Written by: THE BALANCE
Medically reviewed by Dr. Sarah Boss, MD
Last updated: January 20, 2026
Fact checked
Quick Summary
  • One of the most common misconceptions about attention deficit hyperactivity disorder or ADHD is that it only hits children.
  • Estimates suggest that approximately 1.5 million adults in the UK alone have ADHD; however, only 120,000 have been formally diagnosed.
  • If you or a loved one has been experiencing specific symptoms that you think might be because of ADHD, you are not alone.
Reading time: 9 min

One of the most common misconceptions about attention deficit hyperactivity disorder or ADHD is that it only hits children. You might be astonished to learn that it also has a high prevalence in adults. Estimates suggest that approximately 1.5 million adults in the UK alone have ADHD; however, only 120,000 have been formally diagnosed.

If you or a loved one has been experiencing specific symptoms that you think might be because of ADHD, you are not alone. Remember that it’s never too late to talk to a mental health expert and get the diagnosis and treatment you need.

Wondering how to get diagnosed with ADHD as an adult? How is the process initiated, and what exactly does it entail? This article will shed light on the diagnostic criteria and procedure for ADHD in grownups.

Even though there is no single physical, medical, or genetic test for ADHD, experts can perform a diagnostic evaluation by gathering information from different sources. One of the predominant sources to get information from is an ADHD symptom checklist.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) has established guidelines regarding the diagnostic symptoms of ADHD. These guidelines are broadly utilised in clinical practice and research purposes. During an in-depth analysis, a clinician uses these checklists to determine which symptoms currently apply to adults and whether they were present in their childhood. For a positive diagnosis, adults must exhibit at least 5 symptoms.

According to DSM-5, ADHD can present in three different forms, each with its own set of symptoms. These symptoms are mentioned below:

ADHD predominantly inattentive presentation

  • Being extremely forgetful in everyday activities
  • Losing things
  • Getting distracted easily
  • Avoiding tasks that require sustained mental effort
  • Struggling to follow through with instructions
  • Difficulty with organization
  • Failure to pay close attention to details
  • Making careless mistakes
  • Difficulty in sustaining attention

ADHD predominantly hyperactive-impulsive presentation

  • Difficulty remaining seated
  • Fidgeting with feet or hands or squirming in the chair
  • Acting as if being driven by a motor
  • Excessive talking
  • Difficulty engaging in activities in silence
  • Extreme restlessness
  • Constantly interrupting others
  • Blurting out answers before questions are completed
  • Difficulty taking turns or waiting 

ADHD combined presentation

This type of ADHD meets the criteria for both types of presentations.

Keep in mind that the symptoms of ADHD can change with time; hence, adults may present differently from when they were children. A diagnosis can be made based on the severity and number of symptoms, duration, and the degree to which they impair life. Some people successfully meet the diagnostic criteria even without depicting any symptoms of impulsivity or hyperactivity. In such conditions, clinicians often determine if these symptoms are due to another condition or influenced by it.

As one of the most important parts of ADHD evaluation, a structured or semi-structured interview provides clinicians with a detailed history of their patient. The interview includes a pre-determined, standardised set of questions to maximise reliability and reduce variability. During this interview, a clinician covers a vast range of topics, discusses different issues in detail and asks follow-up questions to ensure that no area is left untouched. Then, the examiner reviews the ADHD diagnostic criteria and determines if it applies to the individual in question, both in the present and during childhood. The extent to which the symptoms impair life will also be assessed as part of the interview.      

In addition to determining the diagnosis of ADHD, an examiner will also conduct a detailed evaluation to check for any other psychiatric disorders that may resemble or co-exist with it. According to research, ADHD rarely exists alone, and almost two-thirds of people suffering from it have one or more co-existing issues. The most common issues include learning disabilities, anxiety disorders, substance abuse, and depression. A lot of these conditions can mimic the symptoms of ADHD and sometimes be mistaken for ADHD too. A comprehensive evaluation, thus, aims to screen for these conditions and treat them if found. Failure to diagnose and manage these diseases often leads to failure of ADHD treatment. Moreover, because most ADHD symptoms result from anxiety or depression, failure to detect them may lead to incorrect treatment.

Lastly, the diagnostic evaluation includes questions about the individual’s past medical history and development, going back to early childhood, driving history, academic and work experience, family and social life, and substance abuse history. The aim is to look for any patterns and determine if factors other than ADHD itself are causing symptoms characteristic of this psychiatric illness.

Additional neuropsychological, psychological, or learning abilities testing might be warranted as needed depending on the individual and the nature of their problems. While these additional tests do not play a role in diagnosing ADHD, they can provide helpful information about how this disease affects individuals. The testing can also help clinicians determine if any other co-existing conditions are present. For example, to determine if someone has a learning disability, the assessor will give them a test of intellectual ability and academic achievement.

A medical exam is also recommended if the individual being evaluated has not had a physical exam (within the past 12 months). This exam aims to rule out any medical causes behind the symptoms. Certain medications, such as seizure disorders or thyroid problems, often lead to symptoms that resemble ADHD. While a medical exam cannot confirm the diagnosis of ADHD, it can significantly help rule out other problems.

Towards the end of the assessment, the clinician will integrate all bits and pieces of information they have collected through multiple sources. This integrated information will provide the individuals with diagnostic opinions regarding ADHD and other psychiatric issues that might have been identified during the assessment. This integration of knowledge is followed by an in-depth review of the treatment options by the clinicians. These clinicians also assist the individual in planning psychosocial and medical interventions according to their needs and requirements. This care plan can then be communicated to the individual’s primary care providers as deemed necessary by the clinician.

FAQs

How do I know if I need to get a private ADHD assessment?
Most adults who require an ADHD assessment are the ones experiencing significant problems in one or more aspects of living. Mentioned below are some of the common problems that may suggest getting evaluated:
 
Poor or inconsistent performance in job
Quitting or losing jobs more frequently
A long history of career or academic underachievement
Intense, long-term feelings of stress and worry due to a failure to meet goals and fulfil responsibilities
Forgetting important things
Getting easily upset over minor things
Problems in relationships
An inability to manage daily responsibilities, such as paying bills or completing household chores
What to do if you think you have ADHD?
If you suspect ADHD, the first thing to do is book an appointment with your GP immediately. Discuss with them how you feel, the symptoms you are experiencing, and how they interfere with life. The GP can look into your problem and search for the treatment option available in your area. They may also be able to refer you to a UK private ADHD diagnosis and treatment specialist or a well-being center. If you wish, you can directly contact a private center yourself.
How long does it take to get diagnosed with ADHD?
The criteria for getting an ADHD diagnosis differ for adults and children. A child must display 6 out of 9 set symptoms of impulsiveness and hyperactivity for 6 months continuously to get a diagnosis. On the other hand, adults need to meet a lower threshold of symptoms than children: 5 out of 9 symptoms for at least 6 months. It might be embarrassing for some to discuss their symptoms and problems openly; however, practising honesty can get you the help you need.
Who is qualified to diagnose ADHD?
For adults, the diagnostic evaluation for ADHD must be conducted by a licensed physician or mental health professional. These professionals include psychiatrists, clinical psychologists, neurologists, family doctors, and clinical social workers.
Whichever professional you choose to get an assessment from, remember to ask them about their qualifications and experience in working with ADHD adult patients. In many cases, the expertise and knowledge of an expert about adult ADHD are more critical for establishing an accurate diagnosis followed by a treatment plan than their degree. Qualified professionals can share their training information and experience with their patients. Any reluctance to provide this information must be regarded with suspicion and can indicate that a different specialist must be chosen.
What is the private ADHD diagnosis UK cost on average?
The cost of getting an ADHD diagnosis in the UK may range from £500 – £800 for an assessment. However, bear in mind that in addition to this initial assessment, you may require other short consultations to find out the type of treatment that suits you the best. These consultations can be performed in person or over the telephone and may cost extra (mostly around £125).
How should I prepare for an ADHD assessment?
Feeling a little apprehensive and nervous about getting evaluated for ADHD or any other condition is normal. However, these feelings must not hinder anyone from getting an evaluation, especially if they are facing significant problems in life due to suspected ADHD. Unfortunately, many myths associated with ADHD, such as it only hits children or is not an accurate diagnosis, may make people hesitant to seek help.
Many ADHD assessors request reviewing the old school records and report cards dating back to preschool years to establish a diagnosis. If these records are available, don’t forget to bring them to your first appointment. If applicable, copies of any previous psychological testing must also be taken. Adults who are specifically experiencing problems in their workplace can consider bringing job evaluations with them.
As a part of the assessment, many patients will be asked to complete and return questionnaires. Often, their family members are also asked to participate in these assessments. Make sure to timely complete and return these questionnaires to expedite the evaluation. 
What is a comprehensive evaluation for ADHD?
Different experts can vary in their testing materials and procedures for ADHD diagnosis. However, certain protocols are a mandatory part of a comprehensive evaluation. This usually includes a diagnostic interview, a DSM-5 symptom checklist, and interviews with related people, such as spouses of family members.

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