Newborns can usually take cod liver oil a few days after birth. Cod liver oil contains vitamin A and vitamin D, which can prevent and treat vitamin AD deficiency. Newborns should be supplemented with vitamin A and vitamin D as early as possible after birth, so cod liver oil can be started a few days after birth and can be continued until 3 years of age. Chronic renal failure, hypercalcemia, hyperphosphatemia with renal rickets are prohibited. Cod liver oil should be taken in strict accordance with the doctor’s instructions, and should not be taken in excess. Long-term or overdose can produce chronic poisoning, which can be manifested as bone and joint swelling, itchy skin, dry and cracked lips, fever, vomiting, constipation, diarrhea and so on in the early stage.