Carnitine uptake defect (CUD) is an inborn error of metabolism, an inherited condition in which a carnitine transporter found in the body cannot bring enough carnitine into the cells. Carnitine is a substance made in the body and it can also be found in the diet. Carnitine helps move certain fatty acids into a part of the cells to help the body make energy, and it also helps move toxic substances out of a part of the cells to prevent them from building up. CUD is considered a fatty acid oxidation condition because people affected by CUD have problems using fat as energy for the body. Symptoms of CUD can vary and may include poor feeding, low blood sugar (hypoglycemia), extreme tiredness/lethargy, muscle weakness, liver problems, heart problems, and/or other potential signs and symptoms. CUD can be a life-threatening condition. Management often includes medication/supplements, avoidance of prolonged fasting, and may include other special precautions and emergency recommendations. Support groups are available to help connect families living with CUD with others who have experience or expertise with this condition.