Parenteral nutrition is basically the administration of food or drugs by injection. There are two widely used methods for providing essential nutrients and prescription drugs. One is enteral administration, which is given orally or orally. The other is parenteral, which is given intravenously. In some cases, especially if someone is suffering from a severe eating disorder, parenteral nutrition remains the only effective way to provide essential nutrients. It is also the only cure for indigestion or inability to digest. Peripheral parenteral nutrition solutions are hypertonic to blood and the osmolarity should not exceed 900 mOsm/L. The incidence of phlebitis, inflammation, and pain increases significantly when the osmolarity of the solution exceeds 900 mOsm/L. Adding 5000 units of heparin to the peripheral parenteral nutrition solution may prolong the duration of peripheral infusion. Parenteral nutrition is most often given via central venous access. Catheter insertion site and catheter type must be selected individually. If the purpose of the procedure is to provide only one line of parenteral nutrition, a single lumen catheter is preferred. In general, the preferred insertion site is the subclavian vein. It can be placed if the planned duration of parenteral nutrition exceeds 2 weeks and can be used for up to 6 months in stable patients. The main advantage of these catheters is that they avoid the risks associated with central venous puncture, but they can increase the incidence of phlebitis. Prior to vascular access, the patient should be well hydrated and checked for coagulation status. Strict aseptic technique is required and correct catheter placement should be confirmed with a chest x-ray before starting parenteral nutrition. Proper care of a catheter includes regular examination of the insertion site and dressing with gauze or a transparent, semi-permeable dressing. Mechanical complications during placement include arterial puncture, pneumothorax, and hematoma. Infectious complications associated with central venous access occur in 4-20% of hospitalized patients, especially in immunocompromised and critically ill patients. In patients receiving parenteral nutrition, evidence of fever or sepsis raises suspicion of catheter-related sepsis or catheter infection. Thrombosis detected by ultrasound is common, but its clinical relevance remains unclear. The composition of a parenteral nutrition solution depends on the intravenous site to which it is administered. Peripheral parenteral nutrition (PPN) is usually reserved for patients who require short-term therapy, who do not have significant hypermetabolism or fluid restriction, and who have adequate peripheral venous access. Hypertonic solutions can contribute to phlebitis. Therefore, the osmolality of parenteral nutrition solutions should be less than 900 mOsm/L. This generally requires the use of a 3-in-1 or Total Nutrient Blend (TNA), which combines amino acids, dextrose, and an intravenous lipid emulsion in one container. Central parenteral nutrition is indicated for patients who require long-term parenteral nutrition, who have increased nutritional and metabolic needs, and/or who are fluidly restricted. Parenteral nutrition solutions are administered centrally where blood flow is rapid and osmotic pressure is not a factor. Solutions can be based on glucose (glucose and amino acids) or TNA. Parenteral nutrition may be unavoidable in older people who do not have a functioning gastrointestinal tract. All patients receiving parenteral nutrition should be closely monitored for side effects. Peripheral nutrition can be used for short-term intravenous feeding. A diet with low osmolarity and low risk of soft tissue toxicity is best suited for this purpose.