What Lab Tests Are Done Before Diagnosing ADHD?

PostedSeptember 11, 2025

UpdatedSeptember 11, 2025

ByMy Patient Advice

Author: Harriet Winslow, BSc | Reviewed by: Dr. Rebecca Fernandez, MBBS

Lab tests before ADHD diagnosis can play an important role in ruling out other potential causes of symptoms. While ADHD is primarily diagnosed based on behavioural symptoms, certain medical tests are used to ensure that other conditions are not contributing to the symptoms, such as thyroid issues, anaemia, or hearing problems.

Before diagnosing ADHD, healthcare providers may recommend several tests to eliminate other conditions that could mimic ADHD-like symptoms. For example, a thyroid test can identify hormonal imbalances that may cause irritability, inattention, and fatigue, which can overlap with ADHD symptoms. Similarly, testing for anaemia can help determine whether fatigue or difficulty concentrating is related to low iron levels rather than an attention disorder. Hearing tests may also be conducted to rule out hearing impairments that could lead to misunderstandings or misinterpretations of instructions, leading to behaviours that resemble ADHD.

Common Symptoms: Lab Tests Before ADHD Diagnosis

Thyroid

A thyroid test is crucial as thyroid imbalances can lead to mood swings, inattention, and fatigue, which could be mistaken for ADHD.

Anaemia

Anaemia can cause focus difficulties and lethargy, which might appear similar to ADHD symptoms, so a blood test may be required to rule this out.

Hearing Tests

Hearing tests are important to ensure that hearing loss is not causing inattention or difficulty responding to instructions, which could be mistaken for ADHD symptoms.

By conducting the necessary lab tests before ADHD diagnosis, healthcare providers can ensure an accurate diagnosis and provide appropriate treatment for the individual.

Visit providers like ADHD Certify for personal consultations and expert advice tailored to your needs.

For a deeper dive into the science, diagnosis, and full treatment landscape, read our complete guide to Rule-outs for other conditions.

Harriet Winslow, BSc

Author

Harriet Winslow is a clinical psychologist with a Bachelor’s in Clinical Psychology and extensive experience in behaviour therapy and developmental disorders. She has worked with children and adolescents with ADHD, autism spectrum disorder (ASD), learning disabilities, and behavioural challenges, providing individual and group therapy using evidence-based approaches such as CBT and DBT. Dr. Winslow has developed and implemented personalised treatment plans, conducted formal and informal assessments, and delivered crisis intervention for clients in need of urgent mental health care. Her expertise spans assessment, treatment planning, and behavioural intervention for both neurodevelopmental and mental health conditions.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the author's privacy.

Dr. Rebecca Fernandez, MBBS

Reviewer

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, gynecology, intensive care, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. In psychiatry, Dr. Fernandez has worked with psychotic, mood, anxiety, and substance use disorders, applying evidence-based approaches such as CBT, ACT, and mindfulness-based therapies. Her skills span patient assessment, treatment planning, and the integration of digital health solutions to support mental well-being.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the reviewer's privacy.