Which biochemical marker is used to assess nutritional status? A comprehensive guide

December 23, 2025 •

4 min read

Studies suggest that between 30–50% of hospitalized patients in Western countries experience some degree of malnutrition, making accurate assessment essential for clinical care. This leads to a critical question for clinicians and dietitians: which biochemical marker is used to assess nutritional status accurately and reliably, especially considering confounding factors like inflammation?.

Quick Summary

No single test reliably assesses nutritional status; instead, a panel of biochemical markers, including prealbumin and specific micronutrient assays, must be interpreted alongside clinical data. Inflammation significantly influences many markers, necessitating careful consideration during evaluation.

Key Points

Prealbumin is a marker for acute nutritional changes: Due to its short half-life (2-3 days), prealbumin reflects recent protein intake, making it useful for monitoring immediate responses to nutritional therapy, though it is also a negative acute-phase reactant.
Albumin indicates chronic status but is heavily influenced by inflammation: Its long half-life (14-20 days) makes it a poor measure of short-term changes, and low levels often signify systemic inflammation and disease severity rather than simple malnutrition.
C-reactive protein (CRP) provides context: As a positive acute-phase reactant, CRP rises during inflammation. Measuring CRP alongside visceral proteins like prealbumin helps distinguish between low levels caused by inflammation versus malnutrition.
Micronutrient deficiencies require specific testing: Assessing nutritional status involves targeted tests for specific vitamins (e.g., 25(OH)D for vitamin D) and minerals (e.g., serum ferritin for iron), as overall protein markers do not reflect these levels.
A multi-faceted approach is essential: No single biochemical marker is sufficient for a definitive diagnosis. Combining several markers with a clinical evaluation, dietary history, and anthropometric measurements provides the most accurate picture.
Inflammation is a major confounding factor: Many protein and micronutrient markers are affected by the body's acute-phase inflammatory response, which must be considered during interpretation.

The role of biochemical markers in nutritional assessment

Biochemical assessment involves analyzing biological samples, such as blood and urine, to provide objective data on a person's nutritional state. While powerful, interpreting these markers is complex because they can be influenced by multiple factors beyond diet, such as inflammation, hydration status, and disease. Traditionally, serum proteins like albumin were considered primary indicators of protein-energy malnutrition (PEM), but modern understanding acknowledges their limitations, particularly in the presence of inflammation. A comprehensive approach requires combining various biochemical tests with anthropometric, clinical, and dietary data for an accurate diagnosis.

Protein markers: The visceral proteins

Several serum proteins, primarily synthesized by the liver, serve as markers for protein status. These are often called "visceral proteins." A key challenge is that many are negative acute-phase reactants, meaning their levels decrease during inflammation, infection, or trauma, independent of true nutritional status.

Prealbumin (Transthyretin)

Often considered a more sensitive marker for acute nutritional changes than albumin due to its shorter half-life of approximately 2–3 days. Because of this shorter half-life, prealbumin levels respond more quickly to changes in protein and calorie intake, making it a valuable tool for monitoring the effectiveness of nutritional support. However, its level drops sharply in the presence of inflammation, infection, or liver disease, limiting its use as a sole indicator in acutely ill patients.

Albumin

For decades, serum albumin was a standard marker for nutritional status. It is the most abundant protein in the blood and has a long half-life of 14–20 days. This long half-life makes it a poor indicator of acute nutritional changes. More importantly, albumin is a negative acute-phase reactant, and its levels decrease significantly during systemic inflammation, regardless of a patient's dietary intake. For this reason, low albumin is now considered more of an indicator of disease severity and inflammation than a definitive sign of malnutrition.

Transferrin

Another iron-transporting protein synthesized in the liver with a moderate half-life of about 8–10 days. Like other visceral proteins, its levels are affected by both inflammation and liver disease. It is also directly tied to the body's iron status; transferrin levels increase with iron deficiency and decrease with iron overload. This iron-dependent nature adds another layer of complexity to its interpretation as a nutritional marker.

Inflammatory markers: The indispensable context

Because inflammation confounds the interpretation of visceral protein levels, measuring a marker of the inflammatory response is crucial. The most commonly used marker is C-reactive protein (CRP).

C-reactive protein (CRP)

CRP is a positive acute-phase reactant, meaning its concentration rises rapidly and significantly during inflammation. Measuring CRP alongside prealbumin or albumin helps contextualize their values. For example, a low prealbumin level accompanied by a high CRP level suggests that inflammation, rather than just malnutrition, is driving the low prealbumin reading. The ratio of CRP to albumin or prealbumin has also been studied as a prognostic indicator.

Micronutrient markers: Assessing vitamins and minerals

While protein markers get significant attention, assessing micronutrient status is equally vital. Specific deficiencies require targeted testing.

Iron Status: Serum ferritin, transferrin, and hemoglobin levels are used to assess iron status. Low hemoglobin can indicate iron-deficiency anemia.
Vitamin B12: Total serum vitamin B12 is a common test, but more specific markers like holotranscobalamin (holoTC or 'active B12') and methylmalonic acid (MMA) are also used to assess functional B12 status.
Vitamin D: 25-hydroxyvitamin D (25(OH)D) is the primary marker for assessing vitamin D status and is crucial for bone health.
Zinc: Serum zinc levels are important but challenging to interpret due to the small circulating fraction of total body zinc and its binding to albumin. Low serum zinc can be misleading in the presence of inflammation, which causes zinc redistribution.

Comparison of key biochemical markers


Marker	Half-Life	What It Indicates	Key Limitations
Albumin	14–20 days	Chronic protein status, but more so inflammation and disease severity.	Long half-life makes it insensitive to acute changes. Highly affected by inflammation, liver disease, hydration status.
Prealbumin (Transthyretin)	2–3 days	Recent protein intake and acute changes in nutritional state.	Also a negative acute-phase reactant; levels drop with inflammation, infection, liver dysfunction.
Transferrin	8–10 days	Iron transport and protein status.	Influenced by iron status, liver function, and inflammation.
C-reactive Protein (CRP)	Short half-life	Acute systemic inflammation.	Not a direct nutritional marker; its primary value is contextualizing other protein markers.
25(OH)D	Variable	Vitamin D status.	Influenced by sun exposure, geography, and diet.
Serum Ferritin	Variable	Iron stores.	Can be falsely elevated during inflammation.
Serum B12	Variable	Overall B12 status.	Can be misleading; better functional markers exist.

Considerations for accurate assessment

No single biochemical marker is a magic bullet for nutritional assessment. A multi-marker approach, combined with a comprehensive clinical evaluation, is essential. It is crucial to remember that low levels of visceral proteins like albumin and prealbumin are not always indicative of poor nutrition; they can be a product of the body's inflammatory response to illness or injury. For this reason, assessing inflammation markers like CRP is a standard part of interpreting these results. Similarly, hydration status, renal function, liver function, and a patient's overall disease state must be considered when interpreting any laboratory test.

Conclusion: A multi-faceted approach is key

In conclusion, there is no single biochemical marker that can definitively and accurately assess nutritional status. Instead, a panel of blood and urine tests, including markers for protein status (like prealbumin) and micronutrient levels, must be interpreted holistically. It is imperative to always consider the patient's inflammatory state, using tools like CRP, to properly contextualize the protein markers. This approach, combined with other assessment methods like clinical evaluation and dietary history, provides the most reliable picture of a person's nutritional health, guiding appropriate and timely interventions. For more information, the National Institutes of Health offers extensive resources on nutritional assessment methods.

ncbi.nlm.nih.gov/books/NBK580496/

Authoritative link

For more detailed information on nutritional assessment, a comprehensive overview can be found in the StatPearls collection on the NCBI Bookshelf.

Frequently Asked Questions

Albumin has a long half-life and is a negative acute-phase reactant, meaning its levels drop during inflammation, infection, or trauma. This makes a low albumin level more indicative of disease severity or inflammation than a true reflection of nutritional status alone.

Inflammation causes the liver to reprioritize protein synthesis, decreasing production of negative acute-phase reactants like albumin and prealbumin, while increasing positive ones like CRP. This shifts protein levels in a way that can mimic malnutrition, complicating assessment.

Prealbumin is more sensitive to acute changes due to its shorter half-life (2-3 days) compared to albumin. However, it is still affected by inflammation, so it is not a perfect indicator and must be interpreted with caution, especially in acutely ill patients.

CRP, a marker of inflammation, provides crucial context when interpreting visceral protein levels. A low prealbumin combined with a high CRP suggests inflammation is the primary cause of the low protein level, not malnutrition.

For iron, serum ferritin and hemoglobin are measured. For vitamin D, the test is 25-hydroxyvitamin D. For vitamin B12, serum levels are checked, along with functional markers like holotranscobalamin (holoTC) and methylmalonic acid (MMA).

A single marker is limited by its half-life, sensitivity to inflammation, and specificity. A panel of tests, including various proteins, micronutrients, and inflammatory markers, provides a more comprehensive and accurate picture of a patient's nutritional health.

Yes, many biochemical markers are affected by factors such as hydration status, kidney and liver function, medication use, age, gender, and underlying chronic diseases, which must all be considered during interpretation.