hello dear thanks for your query at health care magic. i understand your concern regarding child. there are multiple causes for lethargic child 1 it can be due low glucose levels because he may not eaten any thing , give him something to eat, 2 it can be due to any poisoning or medicine that you keep in home , child may have accidentaly consumed them , rule out anything like that 3 it can be due to infection in body, child is having fever, this supports infection 4 child may be having infection of the brain or meininges . 5 it can be due to trauma , check for nay signs of injury or bleeding. go for simple test blood sugar levels , complete blood picture and ct scan if needed hope this will help you regards