Cod liver oil and dha can be taken together. Cod liver oil is an oil made from the liver of marine fish. The main components of cod liver oil are fat-soluble vitamin A and vitamin D. Cod liver oil is used for the prevention and treatment of vitamin A and D deficiencies, such as rickets, night blindness and pediatric hand and foot convulsions. The main function of vitamin A is to maintain normal growth, reproduction, vision, epithelial tissue integrity and anti-infection immunity of the body. The main function of vitamin D is to promote the absorption of calcium and phosphorus by the small intestinal mucosa; to promote the reabsorption of calcium and phosphorus by the renal tubules. DHA: docosahexaenoic acid, is a very important unsaturated fatty acid for the human body, DHA is a major component of the growth and maintenance of the nervous system cells, is an important component of the brain and retina, DHA has to promote fetal brain development, promote the maturation of retinal photoreceptor cells, enhance brain cell development, anti-inflammatory, lower cholesterol, prevent blood clots, improve the effectiveness of Alzheimer’s disease. Doctors generally recommend that babies start supplementing with cod liver oil half a month after birth, starting with one drop per day and then gradually increasing to a maximum of five drops. For premature babies, twins, or newborns with digestive tract diseases, cod liver oil should be added from the second week after birth, 5 drops per day, and then changed to 3-5 drops after one month. after 2 years old, the dosage of cod liver oil is gradually reduced.