Vitamin D

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Author: Lynne Brodeur, MA, MLS(ASCP)CM
Reviewers: Kevin F. Foley, PhD, DABCC, MT, SC; Krista Moore, MLS(ASCP)CM

This course discusses the role of Vitamin D in the human body and helps differentiate between the various forms of vitamin D. The mechanisms of metabolism of vitamin D are presented along with the role of the laboratory in the testing for vitamin D. The analytical variables that may affect vitamin D testing are also discussed in this course.

Continuing Education Credits


  • Differentiate between the various forms of vitamin D.
  • Explain the mechanisms of metabolism of vitamin D.
  • Discuss vitamin D deficiency, screening, and risk factors.
  • List the various methodologies for testing vitamin D.
  • List the analytical variables that may affect vitamin D testing.

Course Outline

  • The Different Forms of Vitamin D
      • Role of Vitamin D
      • Receptors
      • Vitamin D Forms
      • Vitamin D2 Form
      • Vitamin D3 Form
      • Vitamin D is considered biologically inactive until it undergoes two enzymatic hydroxylation reactions. Where do these reactions take place?
      • The active form of vitamin D is called:
  • Vitamin D Sources and Metabolism
      • Sources
      • Metabolism
      • Absorption and Excretion
      • Recommended Daily Intake of Vitamin D
      • According to the Institute of Medicine (IOM), what is the recommended dietary allowance of vitamin D for a 65 year old person?
      • How much vitamin D is absorbed depends upon the presence of what substance?
  • Causes of Vitamin D Deficiency
      • Decreased Intake
      • Sunlight and Skin Pigmentation
      • Sunscreen
      • Age
      • Absorption Issues
      • Renal Disease
      • Which one of these patients is most likely to be deficient in vitamin D?
      • Which of the following factors could result in a decrease in vitamin D?
  • Diseases Associated with Decreased Vitamin D
      • Children (Growth and Development)
      • Hyperparathyroidism
      • Osteoporosis and Osteopenia
      • Immune System Impairment
      • Rickets
      • Vitamin D is NOT responsible for building strong bones and teeth in children.
      • Dorothy is a 70-year-old female with the following test results:Vitamin D = 9 ng/mL (20 - 50 ng/mL)Calcium = 7.0 mg/dL (8.5 - 10 mg/dL)Based upon thes...
  • Vitamin D Testing Methods and Methodologies
      • Historical Measurements
      • The Reference Method
      • HPLC
      • Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
      • Immunoassays
      • Sample Requirements
      • Which types of samples would be most appropriate for vitamin D testing?
      • What are some of the advantages of using liquid chromatography tandem mass spectrometry (LC - MS/MS) versus traditional immunoassay techniques?
  • Interferences
      • Medications
      • Antibody and Other Interferences
      • Heterophile antibodies may cause erroneous results in assays that utilize antibodies as their methodology.
      • A patient from the dialysis unit has a vitamin D ordered along with BUN and creatinine. The laboratory request form that accompanies this sample state...
  • References
      • References

Additional Information

Level of Instruction: Intermediate

Intended Audience: Medical laboratory scientists, medical laboratory technicians, pathology residents, MLS students, and other health care personnel who have an interest in this subject matter.

Author Information: Lynne Brodeur, MA, MLS(ASCP)CM holds a master of arts degree in teaching. She is currently a full time lecturer at the University of Massachusetts Dartmouth and works per diem in Clinical Chemistry at St. Luke's Hospital in New Bedford, MA.

Reviewer Information:  Kevin F. Foley, PhD, DABCC, MT, SC is the director of clinical pathology for the Kaiser Permanente Northwest region. He also teaches clinical chemistry at Oregon Health Sciences University. Dr. Foley earned his PhD in clinical pharmacology and toxicology at East Carolina School of Medicine in North Carolina.

Reviewer Information: Krista M. Moore, MLS(ASCP)CM is a Technical Specialist for Chemistry, Immunology, and Toxicology at Kaiser Permanente, Portland, Oregon. She holds BS degrees in Clinical Laboratory Science from Oregon Health Science University/Oregon Institute of Technology and in Chemistry from State University of NY at Geneseo. 

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This course is part of:
Vitamin D2 compound
Vitamin D3 Structure
vitamin D metabolism