Synonym: 25-Hydroxyvitamin D2 and D3, Serum


What this test is useful for? What abnormal levels may tell us?


  • Low Vitamin D levels may indicate deficiency. 
  • High Vitamin D levels may indicate excess or hypervitaminosis.
  • Low Vitamin D level in children may confirm the diagnosis of rickets osteomalacia in young adults.


Interpretation. Clinical significance. What answers the test may offer?


  • Low Vitamin D or deficiency may lead to osteoporosis or brittle bones. Previously it was thought that osteoporosis is a disease of old age. That is not the case. Many young adults and children suffer from that as well.
  • Vitamin D is, mainly, being produced in our body after exposure to the sun. Some of it comes from egg yolks, red meat, salmon, sardines, mackerel, herrings, liver.
  • Other, not fully understood effects of the lack of Vitamin D may be: a) getting frequent infections such as colds, flu or urinary tract infections; b) Feeling fatigued and tired; c) bone and back pain; d) depression; e) Wounds do not heal well; f) hair loss; g) muscle pain; h) inability to lose weight when overweight. 

Clinical references.


  1. Jones G, Strugnell SA, DeLuca HF: Current understanding of the molecular actions of vitamin D. Physiol Rev 1998 Oct;78(4):1193-1231
  2. Miller WL, Portale AA: Genetic causes of rickets. Curr Opin Pediatr 1999 Aug;11(4):333-339
  3. Vieth R: Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr 1999 May;69(5):842-856
  4. Vieth R, Ladak Y, Walfish PG: Age-related changes in the 25-hydroxyvitamin D versus parathyroid hormone relationship suggest a different reason why older adults require more vitamin D. J Clin Endocrinol Metab 2003 Jan;88(1):185-191
  5. Wharton B, Bishop N: Rickets. Lancet 2003 Oct 25;362(9393):1389-1400
  6. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Edited by AC Ross, CL Taylor, AL Yaktine, HB Del Valle. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC. National Academies Press (US), 2011 Available from:
  7. H Rasheed 1, D Mahgoub, R Hegazy, M El-Komy, R Abdel Hay, M A Hamid, E Hamdy, Serum ferritin and vitamin d in female hair loss: do they play a role? 2013;26(2):101-7. doi: 10.1159/000346698. Epub 2013 Feb 20