How is Malnutrition Diagnosed in Adults?

December 5, 2025 •

2 min read

According to the Global Leadership Initiative on Malnutrition (GLIM), a two-step approach is recommended for diagnosing malnutrition in adults, starting with screening to identify at-risk individuals. This process combines an evaluation of a person's medical history with physical examinations and objective measurements to determine nutritional status.

Quick Summary

A proper diagnosis for adult malnutrition involves a multi-faceted approach, assessing weight changes, food intake, body mass index, and inflammation status, often guided by criteria like GLIM or AAIM. Comprehensive physical and laboratory examinations help confirm the diagnosis and determine the severity.

Key Points

Two-Step Diagnosis: Diagnosis follows a two-step process: initial screening identifies at-risk individuals, followed by a comprehensive assessment.
Phenotypic Criteria: Observable signs like unintentional weight loss, a low Body Mass Index (BMI), and reduced muscle mass are key to diagnosis.
Etiologic Factors: Reduced food intake or assimilation, as well as disease-related inflammation, are crucial for determining the underlying cause.
Comprehensive Assessment: A detailed medical history, physical examination for visible signs like fat and muscle loss, and anthropometric measurements are all essential.
Lab Tests: Blood tests for markers like albumin, prealbumin, and C-reactive protein, as well as specific micronutrient levels, provide objective data.
Established Criteria: Global guidelines, including the Global Leadership Initiative on Malnutrition (GLIM), provide a standardized framework for consistent diagnosis and severity grading.
Impact of Inflammation: Understanding whether inflammation is present helps categorize malnutrition and tailor the treatment approach.
Holistic Approach: Accurate diagnosis requires combining subjective patient information with objective clinical, anthropometric, and laboratory data.

Diagnosing malnutrition in adults is a comprehensive process that moves beyond a simple visual assessment. It involves a systematic approach that typically begins with screening and is followed by a detailed assessment using established clinical criteria. This method ensures that all relevant factors—from physical signs to medical history and inflammation—are taken into account for an accurate diagnosis and treatment plan.

The Two-Step Diagnostic Process

The most widely recognized approach for diagnosing malnutrition, developed by the Global Leadership Initiative on Malnutrition (GLIM), involves two main steps: screening and assessment.

Step 1: Screening for Malnutrition Risk

Initial screening is a quick process designed to identify individuals who are at risk. Validated tools such as the Malnutrition Universal Screening Tool (MUST) or the Mini Nutritional Assessment (MNA) for the elderly are used. A positive screening result necessitates a more detailed assessment.

Step 2: Comprehensive Assessment for Diagnosis

If screening indicates risk, a full nutritional assessment is performed. The GLIM criteria require at least one phenotypic criterion and one etiologic criterion for diagnosis.

Phenotypic Criteria (Observable Signs)

These include unintentional weight loss (moderate: >5% in 6 months, severe: >10% in 6 months), low Body Mass Index (BMI), and reduced muscle mass. Muscle mass can be assessed via physical examination or tools like bioelectrical impedance analysis (BIA).

Etiologic Criteria (Underlying Cause)

Key etiologic factors are reduced food intake or assimilation (due to appetite loss, chewing problems, or malabsorption) and inflammation or disease burden from acute injuries or chronic conditions.

Tools and Techniques Used in Diagnosis

Healthcare professionals combine various tools to diagnose malnutrition.

History and Physical Examination

A detailed history covers weight changes, diet, symptoms, medical history, medications, and social factors. The physical exam checks for fat and muscle loss, particularly around the temples, clavicles, and thighs, as well as signs of vitamin deficiencies.

Anthropometric Measurements

Objective body composition data comes from measurements like Body Mass Index (BMI), Mid-Upper Arm Circumference (MUAC), and Bioelectrical Impedance Analysis (BIA).

Laboratory Tests

Blood and urine tests support clinical findings.

Malnutrition Assessment Tools Comparison

Different tools exist for assessing malnutrition, including the Global Leadership Initiative on Malnutrition (GLIM), Academy of Nutrition and Dietetics/ASPEN Indicators (AAIM), and Subjective Global Assessment (SGA). These tools use varying core criteria, phenotypic and etiologic indicators, and assessment processes to identify malnutrition. For a detailed comparison of these tools, refer to {Link: NIH.gov https://pmc.ncbi.nlm.nih.gov/articles/PMC6438340/}.

Conclusion

Diagnosing malnutrition in adults is a systematic process starting with screening and followed by a comprehensive assessment using criteria like GLIM and AAIM. This involves evaluating physical signs, medical history, underlying diseases, anthropometric data, and laboratory results to accurately diagnose and determine severity. A thorough diagnosis is crucial for effective treatment planning and improving patient outcomes.

Frequently Asked Questions

Primary signs of malnutrition in adults include unintentional weight loss (losing 5-10% or more of body weight over a few months), low Body Mass Index (BMI), reduced muscle mass, loss of appetite, and feeling consistently tired or weak.

Doctors screen for malnutrition using validated tools like the Malnutrition Universal Screening Tool (MUST) or the Mini Nutritional Assessment (MNA) for older adults. These tools involve questions about weight loss, appetite changes, and recent illness.

Inflammation, caused by acute injuries or chronic diseases, is considered an etiologic criterion for diagnosing malnutrition. It affects metabolism and nutrient requirements, helping to categorize the type of malnutrition (e.g., chronic disease-related).

No, blood tests are not sufficient on their own. While levels of proteins like albumin and prealbumin can indicate nutritional issues, they are also influenced by hydration and inflammation, requiring interpretation alongside a full clinical and physical assessment.

GLIM is a global consensus framework for diagnosing malnutrition in clinical settings. It requires the presence of at least one phenotypic criterion (weight loss, low BMI, or reduced muscle mass) and one etiologic criterion (reduced food intake or disease-related inflammation).

Healthcare providers check for muscle wasting by observing and palpating muscle groups, especially around the temples, collarbones, shoulders, and hands. More objective measures like handgrip strength or advanced scans can also be used.

Yes, it is possible for an overweight person to be malnourished. This can occur when someone has an excess of calories but a deficiency in essential micronutrients like vitamins and minerals, a condition sometimes called 'overnutrition'.