• Diagnosis
  • Algorithms
  • Background
  • Lab Tests
  • References
  • Related Content

Indications for Testing

  • Chronic diarrhea, steatorrhea, or preexisting condition that may predispose to malabsorption

Laboratory Testing

  • Initial screening tests
    • CBC
      • Mild anemia frequent; leukocytosis in IBD or infectious etiology
      • Eosinophilia – consider parasitic evaluation
    • Electrolyte panel
    • C-reactive protein (CRP)
  • Liver enzymes, including albumin – low albumin suggests chronic processes
    • TSH – rule out thyroid disease
    • In children and adolescents – cystic fibrosis testing (sweat chloride)
    • Fecal tests – perform in parallel with serum tests
      • Stool culture, ova and parasite – evaluation using GI panel; C. difficile testing if risk factors present
      • Fecal leukocytes – present in IBD, infectious diarrhea
      • Fecal occult blood
      • Fecal fat, qualitative/quantitative
    • Consider celiac testing (tTG antibody testing with IgA level)
    • If differentiating between IBS and IBD – fecal calprotectin
    • If initial test results are abnormal, proceed to testing based on suspected disease (see the Malabsorption Testing Algorithm)
  • Secondary testing
    • Based on clinical history and above test results
    • Hydrogen breath test; serum or urine D-xylose; vitamins A, D, E, B12; pancreatic enzyme analysis

Imaging Studies

  • If initial test results are normal, consider abdominal CT or ultrasound, endoscopy

Differential Diagnosis

  • See causes of malabsorption in Clinical Background

Malabsorption is characterized by the inability to digest or absorb nutrients from the small intestine into the bloodstream and is related to diseases of the pancreas, liver, and intestine.

Causes of Malabsorption

  • Inadequate digestion of nutrients
  • Inadequate absorption of nutrients
    • Shortened bowel or loss of absorptive surface (eg, inflammatory bowel disease [IBD], including ulcerative colitis, Crohn disease, gluten-sensitive enteropathy [Celiac sprue], tropical sprue, lymphoma, surgical loss of functional bowel, blind-loop syndrome, hormonal disorders)
    • Impaired nutrient metabolism (eg, deficiency of intestinal disaccharidases, lactase deficiency)
    • Nutrient-specific transport deficiencies (eg, Hartnup disease)
    • Decreased availability of specific nutrients (eg, vitamin B12 deficiency due to decreased intrinsic factor)
    • Alterations of circulation (eg, mesenteric ischemia, heart failure, portal hypertension, lymphatic obstruction
  • Miscellaneous


  • Nutrient digestion and absorption occur in three phases
    • Luminal phase – breakdown and solubilization of proteins, carbohydrates, and fats by digestive enzymes and bile
    • Mucosal phase – transport of digested nutrients into gastrointestinal epithelial cells
    • Transport phase – transport of nutrients via lymphatics and portal circulation from small intestine to other parts of the body
  • Any process that disrupts one or more of these phases can cause malabsorption

Clinical Presentation

  • Prominent symptom – chronic diarrhea
  • Constitutional – weight loss, fatigue
  • Gastrointestinal – steatorrhea, abdominal bloating, abdominal pain, somatostatinoma
  • Extraintestinal – anemia, skin rashes, stomatitis, glossitis, peripheral edema, ascites

Indications for Laboratory Testing

Tests generally appear in the order most useful for common clinical situations.
Click on number for test-specific information in the ARUP Laboratory Test Directory

CBC with Platelet Count 0040002
Method: Automated Cell Count

Electrolyte Panel 0020410
Method: Quantitative Ion-Selective Electrode/Enzymatic

C-Reactive Protein 0050180
Method: Quantitative Immunoturbidimetry

Aspartate Aminotransferase, Serum or Plasma 0020007
Method: Quantitative Enzymatic

Alanine Aminotransferase, Serum or Plasma 0020008
Method: Quantitative Enzymatic

Albumin by Nephelometry 0050671
Method: Quantitative Nephelometry

Thyroid Stimulating Hormone with reflex to Free Thyroxine 2006108
Method: Quantitative Electrochemiluminescent Immunoassay

Occult Blood, Fecal by Immunoassay 2007190
Method: Quantitative Immunoassay

Lactoferrin, Fecal by ELISA 0061164
Method: Qualitative Enzyme-Linked Immunosorbent Assay

Fat, Fecal Qualitative 0020385
Method: Qualitative Microscopy/Stain


Results cannot be used if patient on low-fat diet

Fat, Fecal Quantitative, Homogenized Aliquot 2002350
Method: Nuclear Magnetic Resonance Spectroscopy


Results cannot be used if patient on low-fat diet

Quantitative test requires a 72-hour stool collection

Follow Up

If increased, consider xylose absorption test for assessment of intestinal mucosa integrity

Ova and Parasite Exam, Fecal (Immunocompromised or Travel History) 2002272
Method: Qualitative Concentration/Trichrome Stain/Microscopy


Stool antigen testing is the optimal test method for determining the parasitic presence of Giardia duodenalis (synonyms Giardia lamblia, Giardia intestinalis), Cryptosporidium spp, or Entamoeba histolytica

The ova and parasite exam does not specifically detect Cryptosporidium, Cyclospora, Isospora, and Microsporidia; for Cryptosporidium, refer to the Cryptosporidium Antigen by EIA test; for Cyclospora and Isospora, refer to Parasitology Stain by Modified Acid-Fast; for Microsporidia, refer to Microsporidia Stain

Celiac Disease Reflexive Cascade 2008114
Method: Quantitative Nephelometry/Semi-Quantitative Enzyme-Linked Immunosorbent Assay//Semi-Quantitative Indirect Fluorescent Antibody


EMA-positive sera may show the prozone phenomenon

If antibodies are either very weak or negative at the initial screening dilution, sera will be screened at higher dilutions

Sera containing anti-smooth muscle antibodies (ASMA) will interfere with the detection of EMA IgG; sera should be further tested at higher dilutions

False-negative results

Early disease

Individuals on GFD

Immunoglobulin A 0050340
Method: Quantitative Nephelometry

Tissue Transglutaminase Antibody, IgG 0056009
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay


If antibodies are either very weak or negative at the initial screening dilution, sera will be screened at higher dilutions

False-negative results

Early disease

Individuals on GFD

Pancreatic Elastase, Fecal 0080526
Method: Quantitative Enzyme-Linked Immunosorbent Assay

Follow Up

If pancreatic insufficiency is present, consider cystic fibrosis testing

Xylose Absorption Test (Adult - 5g dose) 0020615
Method: Quantitative Spectrophotometry

Xylose Absorption Test (Adult - 25g dose) 0020609
Method: Quantitative Spectrophotometry

Xylose Absorption Test (Child) 0020612
Method: Quantitative Spectrophotometry

Lactose Tolerance 0020407
Method: Quantitative Enzymatic

Additional Tests Available

Sedimentation Rate, Westergren (ESR) 0040325
Method: Visual Identification


Assesses for inflammatory processes

Elevated in inflammatory or infectious processes

Thyroid Stimulating Hormone 0070145
Method: Quantitative Chemiluminescent Immunoassay


Preferred test for screening and monitoring of thyroid function

Disaccharidase, Tissue 2002247
Method: Quantitative Spectrophotometry


Evaluates patients suffering with chronic diarrhea, intestinal upset, or failure to thrive

Fat, Fecal Quantitative 24-Hour Collection (Includes Homogenization) 2002354
Method: Nuclear Magnetic Resonance Spectroscopy

Fat, Fecal Quantitative 48-Hour Collection (Includes Homogenization) 2002355
Method: Nuclear Magnetic Resonance Spectroscopy

Osmolality, Fecal 0098122
Method: Quantitative Freezing Point

Fat, Fecal Quantitative 72-Hour Collection (Includes Homogenization) 2002356
Method: Nuclear Magnetic Resonance Spectroscopy

Carotenes, Fractionated, Plasma or Serum 0021021
Method: Quantitative High Performance Liquid Chromatography

Electrolytes, Fecal 0060185
Method: Quantitative Ion-Selective Electrode

pH, Fecal 0020518
Method: Quantitative pH Indicator Strips/Quantitative pH Meter

Reducing Substances, Fecal 0020373
Method: Semi-quantitative Colorimetry

Trypsin-Like Immunoreactivity 0070003
Method: Quantitative Radioimmunoassay


Results should be correlated with clinical presentation and other diagnostic data for the diagnosis of pancreatitis

Carotene, Serum Total 0080055
Method: Quantitative Spectrophotometry

Hepatic Function Panel 0020416
Method: Quantitative Enzymatic/Quantitative Spectrophotometry


Initial screening test for hepatobiliary problems

Panel includes albumin; ALP; AST; ALT; bilirubin, direct; protein, total; and bilirubin, total

Vitamin A (Retinol), Serum or Plasma 0080525
Method: Quantitative High Performance Liquid Chromatography

Vitamin D, 25-Hydroxy 0080379
Method: Quantitative Chemiluminescent Immunoassay


Preferred for vitamin D deficiency screening and monitoring

Vitamin E, Serum or Plasma 0080521
Method: Quantitative High Performance Liquid Chromatography

Vitamin B12  0070150
Method: Quantitative Chemiluminescent Immunoassay


Aids in detection of vitamin B12 deficiency in individuals with macrocytic or unexplained anemia, or unexplained neurologic disease

Clostridium difficile toxin B gene (tcdB) by PCR 2002838
Method: Qualitative Polymerase Chain Reaction


Recommended rapid, stand-alone diagnostic test for C. difficile-associated diarrhea


American Society for Clinical Pathology. Choosing Wisely - Five Things Physicians and Patients Should Question. An initiative of the ABIM Foundation. [Last revision Feb 2015; Accessed: Jan 2016]

Holbrook I, British society of Gastroenterology. The British Society of Gastroenterology guidelines for the investigation of chronic diarrhoea, 2nd edition. Ann Clin Biochem. 2005; 42(Pt 3): 170-4. PubMed

General References

Abenavoli L, Proietti I, Vonghia L, Leggio L, Ferrulli A, Capizzi R, Mirijello A, Cardone S, Malandrino N, Leso V, Rotoli M, Amerio P, Gasbarrini G, Addolorato G. Intestinal malabsorption and skin diseases. Dig Dis. 2008; 26(2): 167-74. PubMed

Ammoury R, Croffie J. Malabsorptive disorders of childhood. Pediatr Rev. 2010; 31(10): 407-15; quiz 415-6. PubMed

Chapman T, Chen L, Leaver L. Investigating young adults with chronic diarrhoea in primary care. BMJ. 2015; 350: h573. PubMed

Holt P. Intestinal malabsorption in the elderly. Dig Dis. 2007; 25(2): 144-50. PubMed

Juckett G, Trivedi R. Evaluation of chronic diarrhea. Am Fam Physician. 2011; 84(10): 1119-26. PubMed

Montalto M, Santoro L, D'Onofrio F, Curigliano V, Visca D, Gallo A, Cammarota G, Gasbarrini A, Gasbarrini G. Classification of malabsorption syndromes. Dig Dis. 2008; 26(2): 104-11. PubMed

Schiller L. Diarrhea and malabsorption in the elderly. Gastroenterol Clin North Am. 2009; 38(3): 481-502. PubMed

Schiller L. Management of diarrhea in clinical practice: strategies for primary care physicians. Rev Gastroenterol Disord. 2007; 7 Suppl 3: S27-38. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

Medical Reviewers

Last Update: December 2015