Total Parenteral Nutrition (TPN) and How It Works

Most people receive the energy and nutrients they need through their diets, but sometimes this is not possible for medical reasons. Parenteral nutrition gives a person the nutrients and calories they need through a vein instead of through eating.

With total parenteral nutrition (usually called TPN), a person gets 100% of the nutrition they need each day through a vein.

Parenteral nutrition can be given temporarily or for a longer time. In the United States, around 40,000 people rely completely on feedings given directly through their veins to get the nutrition they need.

What Is TPN Nutrition?

A person who is on total parenteral nutrition receives all the nutrients and energy they need through an intravenous (IV) line. The nutrients enter through the veins and travel through the blood vessels to the entire body.

Normally, the organs of the gastrointestinal tract (especially the small intestine) absorb the calories and nutrients the body needs. Parenteral nutrition completely bypasses the stomach and intestines. Instead, the nutrients are made available directly to the veins, from which they can be pumped all over the body.

You might also hear the term “partial parenteral nutrition.” This refers to someone who is receiving some, but not all, of their total nutrition through their veins. A healthcare provider may prefer this method if a person's gut is impaired but can still perform some digestion.

What Are the Types of TPN Nutrition?

There are two types of TPN nutrition:

Total Parental Nutrition (TPN)

Total parenteral nutrition (TPN) is a method of feeding that bypasses the digestive system. A special formula given intravenously (through a vein) provides most of the nutrients the body needs. TPN is used when someone can't receive food or fluids by mouth and may be needed for weeks, months, or life depending on the condition that causes a need for TPN.

Partial Parenteral Nutrition (PPN)

Partial parenteral nutrition (PPN) is intravenous feeding that supplements other kinds of feeding. PPN may be used to provide additional calories or nutrients along with nutrition received through the gastrointestinal (GI) tract.

Sometimes, TPN nutrition is categorized according to the type of vein that delivers the nutrition.

Central Parenteral Nutrition (CPN): CPN is delivered through a central vein—usually the superior vena cava located near your collarbone. CPN is used for TPN because the larger vein allows the delivery of a higher concentration of nutrition and calories.

Peripheral Parenteral Nutrition (PPN): PPN is delivered through a smaller, peripheral vein, such as one in your neck, arm, or leg. PPN is used for partial parenteral nutrition because it allows quicker and easier access for a shorter period of time.

TPN Nutrition vs. Enteral Nutrition

A person receiving enteral nutrition is absorbing nutrients through their GI tract whereas TPN is received through veins. Enteral nutrition is delivered through tubes that run from the nose or mouth down to the stomach or intestines or through tubes that are medically inserted into the stomach (gastrostomy or G-tube) or part of the small intestine (jejunostomy or J-tube).

Enteral nutrition is preferred to TPN because it:

• Doesn't disrupt the body’s normal digestive processes
• Has less risk of serious complications
• Causes less inflammation
• Is easier to regulate blood sugar levels
• Is less complicated and less expensive

Enteral nutrition might be recommended for someone who is having difficulty swallowing but has a normally functioning GI tract.

When Is TPN Nutrition Used?

Any person who is unable to get enough calories through their gastrointestinal tract might need to receive TPN. Some medical situations that might require TPN include:

• Cancer (particularly of the digestive tract) or complications from cancer treatment
• Ischemic bowel disease
• Obstruction of the digestive tract
• Inflammatory bowel disease (such as Crohn’s disease or ulcerative colitis)
• People who are malnourished
• Diarrhea in children that has lasted a long time, regardless of its cause
• Birth defects of the digestive tract
• Complications from previous bowel surgery

Some premature infants also need to receive TPN temporarily because their digestive tracts are not mature enough to absorb all the nutrients they need.

Some hospitalized people need TPN if they are unable to eat for an extended period and enteral methods are not possible.

When Is Partial Parenteral Nutrition Used?

PPN may be used in situations where the GI tract is working but additional calories and nutrition are needed, such as:

• Preterm infants
• Very-low-birth-weight infants
• People with long-term hospital stays with malnutrition
• People in the intensive care unit (ICU)

What Does TPN Contain?

TPN is designed to replace all the important nutrients that a person would normally be getting through their diet.

These components include:

• Protein
• Carbohydrates
• Fats
• Vitamins and minerals (e.g., vitamin A)
• Electrolytes (e.g., sodium and potassium)
• Trace elements (e.g., zinc)
• Water

There are many specific formulations available for TPN. Not everyone gets the same components in the same amounts. The TPN that you need will depend on several factors, such as your age and any medical conditions that you have.

Your healthcare team will also determine how many calories you need each day. Registered dietitian nutritionists (RDs/RDNs) recommend a solution that meets the macronutrient and micronutrient needs of an individual, depending on specific characteristics like their weight, conditions being treated, and more.

Your healthcare team will carefully tailor your TPN to you based on your specific circumstances, and they will modify the formulation as needed. This helps reduce the risk of complications from TPN.

A person receiving parenteral nutrition—but not total parenteral nutrition—might only get some of these elements, such as carbohydrates and water.

How Is TPN Treatment Decided?

Before starting TPN, your medical team will assess whether TPN is safe and necessary for you. They’ll also need to do some blood tests to help them decide on the ideal formulation.

You’ll need to get certain blood tests at regular intervals after you start TPN to help your healthcare team monitor for and prevent medical complications.

Blood tests you might need include:

• Complete blood count (CBC)
• Electrolytes
• Blood urea nitrogen (to monitor kidney function)
• Blood sugar (glucose) levels
• Liver tests

Your healthcare provider and likely a registered dietitian nutritionist (RD/RDN) will determine your nutritional needs based on your health history, your body weight, and your lab results.

The blood tests generally need to be done more often at first (sometimes multiple times a day). As a person’s medical situation stabilizes, testing is not needed as frequently. The specific tests that you need will depend on your medical situation.

How Will My TPN Nutrition IV Be Administered?

A catheter—a long thin tube—will be put in one of your veins. Catheters your healthcare team might use include the following:

• Tunneled catheter: A segment of the tube is outside the skin and another portion is under the skin.
• Fully implanted catheter: Sometimes called a port-a-cath, the catheter itself is completely beneath the skin and is accessed with a needle to infuse the parenteral nutrition.
• Peripherally inserted central catheter (PICC line): The catheter is inserted into a vein in your upper arm and threaded into your superior vena cava.

An IV bag containing your nutrition solution is then attached to the catheter and infused over 10 to 12 hours. Parenteral nutrition can be administered in a hospital, long-term care facility, or at home.

Side Effects and Risks of TPN Nutrition

Side effects and risks of TPN nutrition can be caused by catheter issues or the TPN itself. Side effects may include:

• Nausea or vomiting
• Allergic reactions
• Headache
• Back pain
• Sweating
• Dizziness

Catheter complications may include:

• Air embolism
• Pneumothorax
• Hitting an artery instead of a vein
• Nerve damage from incorrect insertion
• Catheter fragment embolism
• Cardiac tamponade (very rare but life-threatening)
• Catheter infections
• Blood clots in the vessels near the catheter
• Pulmonary embolism, pulmonary infection, or post-thrombotic syndrome

Health professionals use a strict protocol to keep germs from entering the catheter line.

Risks and side effects of TPN infusions and/or long-term TPN use may include:

• Electrolyte and fluid imbalances
• Vitamin imbalances
• Hyperglycemia (high blood sugar levels)
• Hypoglycemia (low blood sugar levels)
• Gastrointestinal atrophy due to lack of use
• Gallbladder problems due to lack of stimulation
• Osteopenia or osteoporosis
• Cirrhosis (liver scarring) or liver failure

There are some signs that can indicate complications related to TPN. If you have any of these symptoms while on TPN, call your doctor right away.

• Fever
• Chills
• Stomach pain
• Vomiting
• Unusual swelling
• Redness or pain at the catheter site

If you have serious symptoms, such as sudden chest pain or shortness of breath seek immediate emergency care.

Long-Term Outlook Following TPN Nutrition

How long you need to have TPN depends on your underlying medical condition. Some hospitalized people need TPN for just a few weeks.

Other people may need TPN for months (e.g., for problems related to surgical complications), but eventually discontinue TPN. Others might need to remain on TPN for the rest of their life.

Getting TPN at home instead of in the hospital usually improves a person's quality of life. However, people on TPN often experience diminished quality of life and may develop depression.

It’s natural to miss the enjoyment of eating a good meal and the shared social connection with others that eating brings. It’s important to get the psychological support you need in whatever way feels right for you, including professional counseling.

Summary

Total parenteral nutrition (TPN) is the administration of nutrition and calories through an IV line instead of through eating and the GI tract. The two types of parenteral nutrition, TPN and PPN, are delivered either through a central vein or a peripheral vein. Some people receive parenteral nutrition short-term while others rely on TPN for life. Your healthcare team will provide regular monitoring to ensure you get the necessary nutrients and minimize side effects and complications.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

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By Ruth Jessen Hickman, MD
Dr. Hickman is a freelance medical and health writer specializing in physician news and patient education.

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