The best time for infants to take cod liver oil supplement is about half an hour after breastfeeding in the morning. The main components of cod liver oil are vitamin A and vitamin D, which are fat-soluble vitamins and are poorly absorbed when taken on an empty stomach. In addition, 7-dehydrocholesterol in the skin can be converted into vitamin D under ultraviolet irradiation, and the purpose of cod liver oil supplementation is to prevent and treat vitamin A and vitamin D deficiency. Therefore, it is best to take cod liver oil in the morning after drinking milk, and if natural conditions allow, you can sunbathe for 20-30 minutes to help calcium absorption. Different dosage forms of cod liver oil contain different dosages of vitamin A and vitamin D. When taking cod liver oil, it is necessary to check and read the instructions carefully in order to avoid toxicity, and it is recommended to increase or decrease the dosage according to the doctor’s instructions. In addition, cod liver oil is not the only source of vitamin A and vitamin D for infants; it can also be supplemented by sunlight exposure and complementary foods. Therefore, it is recommended to give infants a varied diet and more outdoor activities to increase sunlight exposure.