Laboratory testing is an objective means of assessing organ function, electrolyte levels and to ensure the patient is receiving the appropriate calorie, carbohydrate and lipid combinations to meet nutritional needs without causing liver or other organ damage.  When receiving parenteral nutrition, the mineral content of the solution largely determines these values. Abnormalities can be recognized and changes made to the TPN formula to correct any abnormalities before they become life threatening.  When a patient is initially placed on TPN, lab and vital signs are usually performed much more frequently. Once the patient is stable blood tests can be performed less often. A suggested monitoring schedule is shown below.