Though toxic levels are generally mentioned as 40,000 IU/day, the upper tolerable level for children is 1000-2000 IU/day. But that is data from children above 1 year of age. The exact toxic dose for newborn babies less than 4 weeks old has not been established yet. However, your child needs to be monitored closely, preferably in a healthcare facility.
Generally children with Vit D toxicity develop HYPERCALCEMIA and its complications. Kindly get your child's serum vitamin D levels done. You may also need to check his serum calcium levels. Watch for vomiting, constipation, loss of appetite, excessive thirst, frequent urination, constipation, abdominal pain, muscle weakness, muscle and joint aches, confusion, and fatigue, as well as more serious consequences like kidney damage.
I would advise that you visit the nearby pediatric emergency immediately.
Saptharishi L G
MD, DM, PGDCRL
Pediatric Emergency & Critical care specialist
Dr. Saptharishi L G