Vitamin D supplementation improved autistic symptoms of hyperactivity, social withdrawal, irritability, communication and reduced inappropriate speech. The study was done in 2016 with Egyptian autistic children with serum borderline vitamin d levels The dose was 300 IU per KG of weight, up to 5,000 IU per day for 4 months. No obvious side effects were noted. The symptoms were assessed by the Autism rating and checklist scales.
Note the dosage was stopped after 4 months. Vitamin d can be toxic in high levels and must be evaluated by serum testing every 4 months.