Ruling-out medical tests
If your insurance covers it, you should consider getting a genetics workup, ideally through a geneticist. Some of the common tests run on children with Autism Spectrum Disorder (ASD) are MTHFR, Fragile X, Rett Syndrome, Wilson's Disease, mitochondrial dysfunction, Chiari 1 and PON1.
You may need to see a neurologist for an Magnetic Resonance Imaging (MRI) or electroencephalogram (EEG), but unless your child has seizures or other neurological conditions, neurologists do not treat autism and co-morbid issues. A pediatric doctor CAN prescribe these tests (so you don’t need to visit the neurologist too), but pediatricians rarely will prescribe the recommended 24+ hour unmedicated electroencephalogram (EEG). Obtain a recommendation or verify the selected doctor will prescribe these before you make an appointment. The standard recommendation, a 20-minute electroencephalogram (EEG), is not recommended unless your child is having grand mal seizures every 15 minutes or more.
Your insurance should cover these tests to rule out any underlying issues which may affect treatment or therapies.