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How is autism diagnosed in children, and what happens at an evaluation?

The steps from first worry to diagnosis, who does evaluations, what happens on the day, and how to prepare.

By The Autism Kit teamClinical review in progress · Updated Sep 27, 2026 · 2 min read
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The short answer

There's no blood test for autism. It's diagnosed by specialists who look at your child's development and behavior: they talk with you, watch your child play and communicate, and often use structured activities and questionnaires. The usual path is developmental monitoring, screening at the 18- and 24-month checkups, then a full evaluation if there are concerns.

Key takeaways
  • There is no medical test. Specialists diagnose by looking at development and behavior. - The usual path: monitoring → screening → full evaluation. - Pediatricians screen at 18 and 24 months. You can ask sooner. - You can start early intervention or school support while you wait.

What are the steps to an autism diagnosis?

The CDC describes three steps.1

  1. Developmental monitoring. You and your child's doctor watch how your child plays, learns, talks and moves over time.
  2. Developmental screening. Short questionnaires at well-child visits compare your child with other children the same age. Autism-specific screening is recommended at 18 and 24 months.2
  3. Developmental evaluation. If screening or your concerns point to autism, a specialist does a full evaluation.

Screening can't diagnose autism. It tells you whether a closer look is needed.2 More on that in Is there an online autism test for my child?

Who can diagnose autism?

Evaluations are done by trained specialists, such as developmental pediatricians, child psychologists, child psychiatrists and pediatric neurologists. Speech-language pathologists and occupational therapists are often part of the team.1

Your pediatrician can refer you. To find one yourself, see How do I find an autism evaluation near me?

What happens at an autism evaluation?

Every clinic is a little different, but most evaluations include:3

  • A conversation with you about pregnancy, development, milestones, behavior, sleep, eating and family history.
  • Watching your child play and communicate, often with structured activities designed to show social communication and play.
  • Questionnaires for you, and sometimes for teachers or daycare staff.
  • Other checks, like hearing, speech and language, or thinking and learning skills, to get the full picture.

At the end, or at a follow-up visit, the clinician explains what they found, whether your child meets criteria for autism, and often a level describing support needs. See What are the levels of autism?

How do I prepare for the evaluation?

Try
  • Bring written examples of what you've noticed
  • Bring short videos of typical and hard moments
  • Bring reports from school, daycare or therapists
  • Bring snacks, a comfort item and something to do while waiting
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  • Coaching your child to "behave" differently than usual
  • Waiting until the day to write down concerns
  • Leaving without knowing the next step

Can we get help before the evaluation?

Yes, and you don't have to wait:

  • Under 3: every state has a free early intervention program that can evaluate your child's development. Children don't need an autism diagnosis to qualify.5
  • 3 and older: you can ask your public school district, in writing, to evaluate your child for special education services.4

These programs look at what your child needs, not only at a diagnosis.

Free printable: appointment notesPDF · 2 pages · what you've noticed, plus questions to ask
Download Free printable: appointment notes

What can I do this week?

0 of 4 done

While you wait, the 2-minute quiz gives you one plan for the hardest part of your child's day.

Common questions

By age 2, a diagnosis by an experienced professional can be considered reliable. Some children are diagnosed earlier, and many are diagnosed later.

Sources

  1. CDC: Diagnosing autism spectrum disorder. https://www.cdc.gov/autism/diagnosis/index.html
  2. CDC: Autism screening for healthcare providers. https://www.cdc.gov/autism/hcp/diagnosis/screening.html
  3. HealthyChildren.org (American Academy of Pediatrics): Diagnosing autism. https://www.healthychildren.org/English/health-issues/conditions/Autism/Pages/Diagnosing-Autism.aspx
  4. Center for Parent Information and Resources: Evaluating children for disability (IDEA). https://www.parentcenterhub.org/evaluation/
  5. Early Childhood Technical Assistance Center: State Part C (early intervention) coordinators. https://ectacenter.org/contact/ptccoord.asp

Clinical review in progress: this guide will be reviewed by a board-certified behavior analyst. How we write and review our guides.

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