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What is malnutrition?

Malnutrition basically means “bad nutrition” and is a condition in which there is a disparity between the amount of food and other nutrients that the body needs for proper growth and health and the amount that it receives or takes in (absorbs). This imbalance is most frequently associated with undernutrition, the primary focus of this article, but it may also be due to overnutrition.

Chronic overnutrition can lead to obesity and to metabolic syndrome, a set of risk factors characterized by abdominal obesity, a decreased ability to process glucose (insulin resistance), unhealthy lipid levels, and high blood pressure (hypertension). People with metabolic syndrome have been shown to be at a greater risk of developing type 2 diabetes and cardiovascular disease. Another uncommon form of overnutrition is vitamin or mineral toxicity. This is usually due to excessive supplementation, for instance, with high doses of fat-soluble vitamins such as vitamin A rather than the ingestion of food. Toxicity symptoms depend on the substance(s) ingested, the severity of the overdose, and whether it is acute or chronic.

Undernutrition occurs when one or more vital nutrients are not present or available in the quantity that is needed for the body to develop and function normally. This may be due to insufficient intake, increased loss, increased demand, or a condition or disease that decreases the body’s ability to digest and absorb nutrients from food. While the need for adequate nutrition is a constant, the demands of the body will vary over time.

  • During pregnancy, adequate nutritional support is crucial for normal growth and development of the fetus. A deficiency in folic acid during pregnancy can cause birth defects and increase the risk of low birth weight and preterm delivery.
  • Children can develop a condition called marasmus, a severe deficiency of calories and protein, as a result of a severe shortage of food. Marasmus is characterized by a thin body and stunted growth. If enough calories are given but the food is lacking in protein, a child may develop kwashiorkor, a condition characterized by fluid accumulation (edema), an enlarged liver, apathy, and delayed development. Deficiencies of specific vitamins can also affect bone and tissue formation. A lack of vitamin D, for instance, can affect bone formation, causing rickets in children. Worldwide, about one-third of all childhood deaths are linked to malnutrition. Food shortages and intestinal parasites are leading causes of malnutrition in the developing world. In the U.S., most cases of malnutrition can be attributed to poor or imbalanced diets.
  • Acute conditions such as surgery, severe burns, infections, and trauma can drastically increase short-term nutritional requirements. People who have been malnourished for some time may have weakened immune systems and a poorer prognosis. They frequently take longer to heal from surgical procedures and must spend more days in the hospital. For this reason, many doctors screen and then monitor the nutritional status of their hospitalized patients. Patients having surgery are frequently evaluated both prior to surgery and during their recovery process.
  • Chronic diseases may be associated with nutrient loss, increased nutrient demand, and/or malabsorption. Malabsorption may occur with chronic diseases such as celiac disease, cystic fibrosis, pancreatic insufficiency, and pernicious anemia. An increased loss of nutrients may be seen with chronic kidney disease, diarrhea and excessive bleeding. Sometimes, both the conditions and their treatment can cause malnutrition through decreased intake. An example of this are the decreased appetite, difficulty swallowing, and nausea associated both with cancer (and chemotherapy). People who chronically abuse drugs and/or alcohol might not get enough nutrients, lose too many nutrients and/or cannot absorb a sufficient amount of nutrients.
  • Elderly people require fewer calories but continue to require adequate nutritional support. They are often less able to absorb nutrients due in part to decreased stomach acid production and are more likely to have one or more chronic ailments that may affect their nutritional status. At the same time, they may have more difficulty preparing meals and may have less access to a variety of nutritious foods. Older people also frequently eat less due to a decreased appetite, decreased sense of smell, and/or mechanical difficulties with chewing or swallowing.


About malnutrition

Signs and Symptoms

General malnutrition often develops slowly, over months or years. As the body’s store of nutrients is depleted, changes begin to happen at the cellular level, affecting biochemical processes and decreasing the body’s ability to fight infections. Over time, a variety of symptoms may begin to emerge, including:

  • In children, delayed or slow growth, bloated abdomen, listlessness
  • Anemia
  • Weight loss, decreased muscle mass, and weakness
  • Dry scaly skin
  • Fluid accumulation (edema)
  • Brittle, thinning hair
  • Brittle and malformed (spooned) nails
  • Chronic diarrhea
  • Slow wound healing
  • Bone and joint pain
  • Mental changes such as confusion and irritability
  • Enlarged thyroid gland (goiter)

Specific nutrient deficiencies may cause characteristic symptoms. For instance, vitamin B12 deficiency can lead to tingling, numbness, and burning in the hands and feet (due to nerve damage); a lack of vitamin A may cause night blindness and increased sensitivity to light; and a lack of vitamin D can cause bone pain, malformation, or osteomalacia. The severity of symptoms depends on the intensity and duration of the deficiency. Some changes, such as to bone and nerves, may be irreversible.


Malnutrition will often be noticeable to the doctor’s trained eye before it causes significant abnormalities in laboratory test results. During physical examinations, a health practitioner will evaluate an individual’s overall appearance: their skin and muscle tone, the amount of body fat they have, their height and weight, and their eating habits. In the case of infants and children, doctors will look for normal development and a normal rate of growth.

If there are signs of malnutrition, a healthcare practitioner may order laboratory screening tests to evaluate a person’s blood and organ function. Additional individual tests may be ordered to look for specific vitamin and mineral deficiencies. If general malnutrition and/or specific deficiencies are diagnosed, then laboratory testing may be used to monitor the response to therapy. A person who has malnutrition because of a chronic disease may need to have his or her nutritional status monitored on a regular basis.

Hospitalized patients are often assessed for nutritional status prior to or at the time of admission. This may include a history, an interview by a dietician, and laboratory tests. If the results of these tests indicate possible nutritional deficits, patients may be provided nutritional support prior to a surgery or procedure and be monitored regularly during recovery.

Laboratory tests may include:
For general screening and monitoring:

For nutritional status and deficiencies:

  • Iron tests such as serum iron, transferrin and iron-binding capacity, and ferritin
  • Vitamins and trace minerals such as B12 and folate, vitamin Avitamin D, B vitaminscalcium, and magnesium
  • Prealbumin: although commonly used as a marker of malnutrition, levels of this protein may be affected by a number of conditions other than malnutrition. Research is continuing in order to better understand the role(s) of prealbumin in the body, especially the reasons for changes observed during illness, and the clinical utility of prealbumin testing.
  • Albumin has been used in the past along with or instead of prealbumin to evaluate nutritional status but now is more often used to screen for and help diagnose liver or kidney disease.
  • Leptin: suppressed levels may indicate malnutrition in some patients; this test is not widely available.
  • Celiac disease blood tests measure the amount of particular antibodies in the blood. The most common tests include anti-tissue transglutaminase (tTG), IgA class, quantitative immunoglobulin A (IgA) test, and deamidated gliadin peptide antibodies (anti-DGP), IgA or IgG.

Non-laboratory tests
Imaging and radiographic scans may be ordered to help evaluate the health of internal organs and the normal growth and development of muscles and bones. These tests may include:

  • X-rays
  • CT (Computed Tomography)
  • MRI (Magnetic Resonance Imaging)

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Treatment of undernutrition includes:

  • Restoring the nutrients that are missing, making nutrient-rich foods available, and providing supplements for specific deficiencies. In someone who is severely malnourished, this must be done slowly until the body has had time to adjust to the increased intake and then maintained at a higher than normal level until a normal or near normal weight has been achieved.
  • Regular monitoring of those patients who have chronic malabsorption disorders or protein- or nutrient-losing conditions. Once the deficiencies have been addressed, putting a treatment plan into place is needed to prevent the malnutrition from recurring.

See the Related Content section below for links to treatment information.

View Sources

Sources Used in Current Review

World Health Organization. (May 2017 updated.) Malnutrition Fact Sheet. Available online at Accessed July 18, 2017.

Shashidhar HR. (23 June 2017 updated.) Malnutrition. Available online at Accessed July 16, 2017.

Morley, JE. Undernutrition. Available at Accessed July 18, 2017.

National Institute of Diabetes and Digestive and Kidney Diseases. (September 2013 updated.) Celiac Disease Testing (for Health Care Professionals). Available online at Accessed July 21, 2017.

National Health Service. (2 February 2017 updated.) Malnutrition. Available online at Accessed July 16, 2017.

Sources Used in Previous Reviews

John Hopkins Children’s Center. Malnutrition. Available online at Accessed February 2013.

(©2013 WHO) World Health Organization. Parasitic Diseases. Available online at Accessed March 2013.

(©2013 WHO) World Health Organization. Malnutrition. Available online at Accessed March 2013.

Amirkalali, B., Sharifi F., Fakhrzadeh, H., Mirarefein, M., Ghaderpanahi, M., Badamchizadeh, Z., Larijani, B. (2010 May) Low serum leptin serves as a biomarker of malnutrition in elderly patients. Endocrinology and Metabolism Research Institute. Available online at Accessed February 2013.

Föcker, M., Timmesfeld, N., Scherag, S., Bühren, K., Langkamp, M., Dempfle, A., Sheridan, E., de Zwaan, M., Fleischhaker, C., Herzog, W., Egberts, K., Zipfel, S., Herpertz-Dahlmann, B., Hebebrand, J. Screening for anorexia nervosa via measurement of serum leptin levels. Available online at Accessed February 2013.

Parrish, C. Serum proteins as markers of nutrition: what are we treating? Practical Gastroenterology. October 2006. Available online through Accessed March 2013.

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Malnutrition in the Elderly. Nutrition Screening Initiative [On-line information]. Available online at through

Beck, F. and Rosenthal, T. (2002 April 15). Prealbumin: A Marker for Nutritional Evaluation [24 paragraphs]. American Family Physician [On-line journal]. Available online at through

Beck, F. and Rosenthal, T. (2002 April 15). Evaluation and Treatment of Weight Loss in Adults with HIV Disease. American Family Physician [On-line journal]. Available online at through

Krugman, S. and Dubowitz, H. (2003 September 1). Failure to Thrive. American Family Physician [On-line journal]. Available online at through

Chapter 2. Malnutrition. Merck Manual of Diagnosis and Therapy, Section 1. Nutritional Disorders [On-line journal]. Available online at through

Evans, W. (2001 September 24). Aging and Malnutrition: Treatment Guidelines. Medscape Today, Clinical Update [On-line information and CME]. Available online at through

Polsdorfer, J. Starvation. AccessMed Health Information Library [On-line information]. Available online at through

Demling, R. and DeSanti, L. (2001). Involuntary Weight Loss and Protein-Energy Malnutrition: Diagnosis and Treatment. Medscape Today, Clinical Update [On-line information and CME]. Available online at through

Fyke, M. Malnutrition. AccessMED Health Information Library [On-line information]. Available online at through

Webner, D. (2003 September 8, Updated). Malnutrition. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at