From the Guidelines
Basic labs to assess nutritional deficiencies include a complete blood count (CBC), comprehensive metabolic panel (CMP), vitamin D level, vitamin B12, folate, iron studies, zinc, magnesium, and albumin/prealbumin. These tests are essential in identifying nutritional deficiencies, as they provide valuable information about a patient's metabolic status, electrolyte balance, and protein levels 1. A CBC can help identify anemia patterns suggestive of iron, B12, or folate deficiency, while a CMP evaluates electrolytes, kidney and liver function. Specific vitamin assays, such as vitamin D and B12, can directly measure levels of crucial nutrients, which are common deficiencies even in developed countries. Iron studies, including ferritin, iron, and total iron binding capacity, can help diagnose iron deficiency before anemia develops. Albumin and prealbumin serve as markers of protein status, although they can be affected by inflammation and other conditions.
Some laboratory tests, such as those that relate to visceral protein concentrations (e.g., hemoglobin, total lymphocyte count), can help identify malnutrition 1. Proteins with shorter half-lives, like pre-albumin or retinol-binding protein, can reflect improving nutritional status better than albumin when sequentially assessed. However, no single protein is ideal as an indicator of nutritional status, as they are all affected by other non-nutritional physiological and pathological states. Other laboratory tests, such as nitrogen excretion, nitrogen balance, and plasma amino acid profile, can help characterize protein deficit but are not commonly used in clinical practice.
For patients with suspected malabsorption or specific dietary restrictions, additional tests might include zinc, selenium, copper, vitamin A, vitamin E, and methylmalonic acid (which helps confirm B12 deficiency) 2. These tests should be ordered based on clinical suspicion, dietary history, and physical examination findings rather than as a universal panel, as targeted testing is more cost-effective and clinically useful. The Institute of Medicine's recommended dietary allowances (RDAs) and tolerable upper intake levels (ULs) for certain vitamins and minerals can guide the interpretation of laboratory results and help identify potential deficiencies 2.
Key points to consider when assessing nutritional deficiencies include:
- Using a combination of laboratory tests to evaluate nutritional status
- Considering the patient's clinical history, dietary habits, and physical examination findings when ordering tests
- Targeted testing rather than universal panels to improve cost-effectiveness and clinical utility
- Being aware of the potential limitations and confounding factors of laboratory tests, such as inflammation and other non-nutritional conditions.
From the FDA Drug Label
Hematocrit, reticulocyte count, vitamin B12, folate and iron levels should be obtained prior to treatment. The basic labs to assess for nutritional deficiencies are:
- Hematocrit
- Reticulocyte count
- Vitamin B12 levels
- Folate levels
- Iron levels 3
From the Research
Basic Labs to Assess Nutritional Deficiencies
The following labs are used to assess nutritional deficiencies:
- Full blood count to detect anaemia, which can be caused by a nutritional deficiency of iron, vitamin B12, or folate 4
- Laboratory measurement of the concentration in blood of: + Iron + Vitamin B12 + Folate + Ferritin (to assess iron stores) + Vitamin D (25-hydroxyvitamin D) + Magnesium + HbA1c (to assess blood sugar control) 5
- These labs can help identify deficiencies in vitamins and minerals such as: + Vitamin A + Vitamin B12 + Vitamin D + Calcium + Iron + Folate 6