Diagnosis of malnutrition

Malnutrition is diagnosed based on certain factors like duration and precipitating causes if any. Clinical history and symptoms of malnutrition are often the major determinants of malnutrition and there is little role of diagnostic and imaging studies in evaluation of malnutrition.

Diagnostic tests and imaging studies may be needed to rule out deeper causes or illnesses that may have led to the malnourished state. 1-7

Outline of diagnosis of malnutrition includes BMI, routine blood tests and so forth.

Body mass index (BMI)

This is calculated by the weight in kilograms divided by the height in metres squared. A healthy BMI for adults usually lies between 18.5 and 24.9. Those with a BMI between 17 and 18.5 could be mildly malnourished, those with BMIs between 16 and 18 could be moderately malnourished and those with a BMI less than 16 could be severely malnourished.

Those with a history of unintentionally losing weight over the last few months, those who are unable to feed themselves or those with a health condition that caused lack of adequate nutrition or caused increased demands of nutrients that was not met by regular diet are at risk of malnutrition.

These individuals need to be evaluated carefully. Those who have eaten little or nothing for the last five days or are likely to eat little or nothing for five days or longer, those who cannot absorb nutrients from food well like those with ulcerative colitis or Crohn’s disease, may be at risk.

In general all with a BMI less than 18.5 in a course of few months need to be evaluated. Pregnant women, elderly living in care homes and children are at greater risk.

Routine blood tests

This is done to assess anemia and other vitamin and mineral deficiencies. There may be dehydration, low blood sugar and signs of severe infection as is evident by raised while blood cell counts.

Diagnosis of malnutrition in children

In children weight and height is measured and compared with the charts showing the expected average height and weight for a child of that age. Some children are persistently smaller for age and may be genetically so.

What should alarm parents and caregivers is a sudden or significant drop below the expected level for a child as it may indicate malnutrition. Children who show a slower growth may also be malnourished.

Mid-upper arm diameter

Mid upper arm diameter may be used in children. An upper arm circumference of less than 110 mm is also used to define severe malnutrition in children. In children thickness of skin folds is also measured. With malnutrition there is loss of the fat beneath the skin called the subcutaneous fat. This leads to thin skin folds.

Blood tests in children

Routine blood tests in children include those for blood glucose, blood counts, urine for routine examination, stool for parasites and worm infestations (as these may lead to malnutrition in children), blood protein or albumin levels, HIV test and tests for other infections.

Levels of iron in blood, folic acid and vitamin B 12 are also recommended. For protein estimation other tests include Pre-albumin, transferrin, retinol-binding protein.

Other tests for malnutrition

Other tests include:

  • thyroid function tests
  • estimation of the intestine for Crohn’s disease or Coeliac disease
  • levels of Calcium, Phosphate, Zinc and vitamins
  • low levels of cholesterol and albumin (especially in elderly)

Further Reading

Last Updated: Mar 13, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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