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Nutrition in Clinical Medicine


Adrienne Youdim

, MD, David Geffen School of Medicine at UCLA

Last full review/revision May 2019| Content last modified May 2019
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Nutritional deficiencies can often worsen health outcomes (whether a disorder is present or not), and some disorders (eg, malabsorption) can cause nutritional deficiencies. Also, many patients (eg, older patients during acute hospitalization) have unsuspected nutritional deficiencies that require treatment. Many medical centers have multidisciplinary nutrition support teams of physicians, nurses, dietitians, and pharmacists to help the clinician prevent, diagnose, and treat occult nutritional deficiencies.

Overnutrition may contribute to chronic disorders, such as cancer, hypertension, obesity, diabetes mellitus, and coronary artery disease. Dietary restrictions are necessary in many hereditary metabolic disorders (eg, galactosemia, phenylketonuria).

Evaluation of Nutritional Status

Indications for nutritional evaluation include the following:

  • Undesirable body weight or body composition

  • Suspicion of specific deficiencies or toxicities of essential nutrients

  • In infants and children, insufficient growth or development

Nutritional status should be evaluated routinely as part of the clinical examination for

  • Infants and children

  • Older people

  • People taking several drugs

  • People with psychiatric disorders

  • People with systemic disorders that last longer than several days

Evaluating general nutritional status includes history, physical examination, and sometimes tests. If undernutrition is suspected, laboratory tests (eg, albumin levels) and skin tests for delayed hypersensitivity may be done. Body composition analysis (eg, skinfold measurements, bioelectrical impedance analysis) is used to estimate percentage of body fat and to evaluate obesity.

History includes questions about dietary intake, weight change, and risk factors for nutritional deficiencies and a focused review of systems (see table Symptoms and Signs of Nutritional Deficiency). A dietitian can obtain a more detailed dietary history. It usually includes a list of foods eaten within the previous 24 hours and a food questionnaire. A food diary may be used to record all foods eaten. The weighed ad libitum diet, in which the patient weighs and writes down all foods consumed, is the most accurate record.


Symptoms and Signs of Nutritional Deficiency


Symptom or Sign


General appearance





Many vitamins, zinc, essential fatty acids

Rash in sun-exposed areas

Niacin (pellagra)

Easy bruising

Hair and nails

Thinning or loss of hair

Premature whitening of hair

Spooning (upcurling) of nails


Impaired night vision

Corneal keratomalacia (corneal drying and clouding)


Cheilosis and glossitis

Riboflavin, niacin, pyridoxine, iron

Bleeding gums




Paresthesias or numbness in a stocking-glove distribution

Thiamin (beriberi)


Cognitive and sensory deficits

Thiamin, niacin, pyridoxine, vitamin B12



Wasting of muscle


Bone deformities (eg, bowlegs, knocked knees, curved spine)

Bone tenderness

Joint pain or swelling



Diarrhea and dysgeusia

Dysphagia or odynophagia (due to Plummer-Vinson syndrome)



A complete physical examination, including measurement of height and weight and distribution of body fat, should be done. Body mass index (BMI)—weight(kg)/height(m)2, which adjusts weight for height (see table Body Mass Index), is more accurate than height and weight tables. There are standards for growth and weight gain in infants, children, and adolescents (see Physical Growth of Infants and Children).


Body Mass Index (BMI)

Weight Category


Normal* (18.5–24)

Overweight (25–29)

Obese: Class I (30–34)

Obese: Class II (35–39)

Obese: Class III (≥ 40)


Body Weight

60–61 in (152–155 cm)

97–127 lb (44–58 kg)

128–153 lb (58–69 kg)

153–180 lb (69–82 kg)

179–206 lb (81–93 kg)

>206 lb (>93 kg)

62–63 in (157–160 cm)

104–135 lb (47–61 kg)

136–163 lb (62–74 kg)

164–191 lb (74–87 kg)

191–220 lb (87–100 kg)

>220 lb (>100 kg)

64–65 in (162–165 cm)

110–144 lb (50–65 kg)

145–174 lb (66–79 kg)

174–204 lb (79–93 kg)

204–234 lb (93–106 kg)

>234 lb (>106 kg)

66–67 in (168–170 cm)

118–153 lb (54–69 kg)

155–185 lb (70–84 kg)

186–217 lb (84–98 kg)

216–249 lb (98–113 kg)

>249 lb (>113 kg)

68–69 in (173–175 cm)

125–162 lb (57–74 kg)

164–196 lb (74–89 kg)

197–230 lb (89–104 kg)

230–263 lb (104–119 kg)

>263 lb (>119 kg)

70–71 in (178–180 cm)

132–172 lb (60–78 kg)

174–208 lb (79–94 kg)

209–243 lb (95–110 kg)

243–279 lb (110–127 kg)

>279 lb (>127 kg)

72–73 in (183–185 cm)

140–182 lb (64–83 kg)

184–219 lb (84–99 kg)

221–257 lb (100–117 kg)

258–295 lb (117–134 kg)

>295 lb (>134 kg)

74–75 in (188–190 cm)

148–192 lb (67–87 kg)

194–232 lb (88–105 kg)

233–272 lb (106–123 kg)

272–311 lb (123–141 kg)

>311 lb (>141 kg)

76 in (193 cm)

156–197 lb (71–89 kg)

205–238 lb (93–108 kg)

246–279 lb (112–127 kg)

287–320 lb (130–145 kg)

>320 lb (>145 kg)

*BMIs less than those listed as normal are considered underweight.

Distribution of body fat is important. Disproportionate truncal obesity (ie, waist/hip ratio > 0.8) is associated with cardiovascular and cerebrovascular disorders, hypertension, and diabetes mellitus more often than fat located elsewhere. Measuring waist circumference in patients with a BMI of < 35 helps determine whether they have truncal obesity and helps predict risk of diabetes, hypertension, hypercholesterolemia, and cardiovascular disorders. Risk is increased if waist circumference is > 102 cm (> 40 in) in men or > 88 cm (> 35 in) in women.

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