Quick answer: In Illinois, an autism diagnosis usually follows five steps: (1) you or your pediatrician notice developmental differences, (2) a developmental screening, (3) a referral to Early Intervention (birth–3) or your school district (age 3+), (4) a comprehensive diagnostic evaluation by a qualified professional, and (5) receiving the written diagnosis and starting services such as ABA therapy. The process can take a few weeks to several months—starting early makes a real difference.
What an autism diagnosis actually is
An autism diagnosis is a clinical conclusion that a child's social communication and behavior patterns meet the criteria for autism spectrum disorder (ASD) described in the DSM-5. It is not a label that limits your child—it is a key that unlocks the right therapies, school supports, and insurance coverage. In Illinois, the path to that diagnosis is well established, whether your child is a toddler who isn't babbling yet or a school-age child who struggles socially.
At Green Pediatrics Behavioral Services, we walk North Shore families through this process every week. Below is the same roadmap we share in our free consultations.
Who should be evaluated—and when to act
Trust your instincts. If something feels different about how your child connects, plays, or communicates, an evaluation is worth pursuing. Common early signs include:
- Limited eye contact or little response to their name by 12 months
- Few gestures such as pointing, waving, or showing you objects
- Delayed or absent speech, or loss of words they once used
- Strong preference for routines and distress with small changes
- Repetitive movements such as hand-flapping, rocking, or lining up toys
- Intense, narrow interests or unusual reactions to sounds, textures, or lights
You do not need to wait for a certain age or "see if they grow out of it." For a toddler-specific look at these signs, read our guide to signs of autism in toddlers.
The Illinois autism diagnosis process, step by step
Step 1: Notice and document your concerns
Start a simple list of what you're seeing and when it began. Short phone videos of the behaviors that worry you are genuinely useful to clinicians. This record turns a vague worry into concrete information that speeds up every step that follows.
Step 2: Talk to your pediatrician and complete a screening
The American Academy of Pediatrics recommends autism-specific screening at the 18- and 24-month well-child visits, and any time a parent raises a concern. Your pediatrician will often use a validated tool such as the M-CHAT-R. A screening is not a diagnosis—it simply flags whether a full evaluation is warranted.
Step 3: Get a referral—Early Intervention or your school district
Illinois has two publicly funded doorways, depending on age. Children under three can be referred to the Illinois Early Intervention program through a local Child and Family Connections (CFC) office for a developmental evaluation at little or no cost. For children three and older, your local public school district is required to evaluate for educational eligibility at your written request. You can pursue these alongside a private medical evaluation.
Step 4: The comprehensive diagnostic evaluation
A medical autism diagnosis is made by a qualified professional—typically a developmental pediatrician, child psychologist, neurologist, or psychiatrist. A thorough evaluation usually includes a detailed developmental and family history, direct observation of your child (often using a structured tool such as the ADOS-2), and input from parents and sometimes teachers. Hearing and vision are usually checked first to rule out other explanations.
Step 5: Receive the diagnosis and next steps
You'll receive a written report summarizing the findings, whether or not criteria for ASD were met, along with recommendations. If your child is diagnosed, that report becomes the foundation for insurance authorization, an IEP, and therapies like ABA therapy. If your child was evaluated through a school, you may receive an educational "determination" rather than a medical diagnosis—these serve different purposes, as explained below.
Where to go, by your child's age
| Child's age | Where to start | What you get |
|---|
| Birth–3 years | Illinois Early Intervention (CFC) | Developmental evaluation & in-home services |
| 3–5 years | School district + pediatrician | Educational eligibility & medical referral |
| School age (5+) | School district + medical provider | IEP/504 supports & formal diagnosis |
Why an early diagnosis matters
Acting early gives your child the best possible head start:
- Earlier access to therapy during the years of greatest brain plasticity
- Meaningful gains in communication, play, and daily-living skills
- Coaching for the whole family through parent training
- Smoother school transitions and appropriate classroom accommodations
- Insurance coverage that would otherwise be out of reach
To understand how a support plan is built after diagnosis, see our overview of the functional behavior assessment.
Common misconceptions
- "A diagnosis will limit my child." The opposite is true—it opens doors to support that helps children thrive.
- "They're too young to know." Autism can be reliably identified in many children by age two, and screening starts even earlier.
- "We should just wait and see." Waiting delays therapy during the most important developmental window.
- "A school evaluation is the same as a medical diagnosis." They overlap but are not interchangeable—see the FAQ.
What to expect: timelines and outcomes
Timelines vary. Screening happens in a single visit, while scheduling a full diagnostic evaluation can take anywhere from a few weeks to several months, depending on provider wait times. Illinois Early Intervention is designed to move quickly once you're referred. The outcome you can count on is a clearer picture of your child's strengths and needs, and a concrete plan. Many families tell us the diagnosis itself brought relief—finally, a roadmap.
Wondering about cost? See our guide to insurance and coverage, and don't hesitate to reach out with questions.
Frequently asked questions
How long does it take to get an autism diagnosis in Illinois?
Screening is immediate, but a full diagnostic evaluation may take from a few weeks to several months to schedule, depending on the provider. Referring to Early Intervention (under 3) or your school district (age 3+) can speed access to support while you wait.
Do I need a doctor's referral to start Early Intervention?
No. In Illinois, parents can self-refer to their local Child and Family Connections (CFC) office for an Early Intervention evaluation—you don't need a physician's referral to begin.
Can my child get ABA therapy without a formal autism diagnosis?
Generally, insurance requires a documented autism diagnosis to authorize ABA, which is why completing the evaluation matters. Our team can help you understand what your specific plan requires.
Does a school "educational determination" count as a medical diagnosis?
Not exactly. A school determination establishes eligibility for special-education services, while a medical diagnosis from a physician or psychologist is what insurers typically require for therapies like ABA. Many families obtain both.
How much does an autism evaluation cost, and does insurance cover it?
Costs vary by provider and setting. Early Intervention evaluations are low- or no-cost, and many private evaluations are covered by insurance. Check your plan's benefits—our team is happy to help you navigate them.
Helpful resources
Clinically reviewed by Teba Aijaz, MS, BCBA, LBA, Founder & Clinical Director.
