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Free 25OH Vitamin D ELISA

  • Regulatory status:RUO
  • Type:Sandwich ELISA, HRP-labelled antibody
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Cat. No. Size Price

RKARF1991R 96 wells (1 kit)
PubMed Product Details
Technical Data


Sandwich ELISA, HRP-labelled antibody



Sample Requirements

10 µl/well


At ambient temperature. Upon receipt, store the product at the temperature recommended below.



Calibration Range

35-2.4 pg/ml

Limit of Detection

2,4 pg/ml

Inter-assay (Run-to-Run)

6,1 %



Incubation time: 1h30 min/30 min/ 20 min at 37°C with shaking

Research topic

Bone and cartilage metabolism


Vitamin D is a steroid hormone involved in the intestinal absorption of calcium and the regulation of calcium homeostasis. There are two different forms of Vitamin D, named D3 and D2, which are very similar in structure. The D2 is a synthetic product, which is predominantly absorbed by fortified food. Physiological Vitamin D3 levels result not only from dietary uptake but also by biosynthesis of 7-dehydrocholesterol and UV-light in skin because of sun exposure. Vitamin D deficiency can result from inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders. Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis. Research has indicated that vitamin D deficiency is linked to colon cancer; conflicting evidence links vitamin D deficiency to other forms of cancer. In the liver, the vitamin is hydroxylated to 25-hydroxyvitamin D (25-OH Vitamin D), the major circulating metabolite of Vitamin D. Although 1,25-(OH)2 Vitamin D portrays the biological active form of Vitamin D, which is synthesized in the kidney, it is widely accepted that the measurement of circulating 25-OH Vitamin D provides better information with respect to patients Vitamin D status and allows its use in diagnose hypovitaminosis . The concentration of 25-OH Vitamin D decreases with age and a deficiency is common among elderly persons. Clinical applications of 25-OH Vitamin D measurements are the diagnosis and therapy control of postmenopausal osteoporosis, rickets, osteomalacia, renal osteodystrophy, pregnancy, neonatal hypocalcemia and hyperparathyro­idism. Vitamin D intoxication mostly occurs during a large intake of pharmaceutical preparations of Vitamin D and may lead to hypercalcemia, hypercalcuria and nephrocalcinosis in susceptible infants.

References to Product


  • BIKLE D. (2013), Variability in free 25(OH) vitamin D levels in clinical populations, J. Steroid Biochem. Mol. Biol., S09600760.
  • BIKLE D., Gee E, Halloran B, Haddad JG. Free 1,25-dihydroxyvitamin D levels in serum from normal subjects, pregnant subjects, and subjects with liver disease. J Clin Invest 1984;74:1966–71.
  • BOUILLON R. (2016), Free 25-hydroxyvitamin D: impact of vitamin D binding protein assays on racial genotypic associations, JCEM,
  • SCHWARTZ J.B. (2014), A comparison of direct and calculated free 25(OH) Vitamin D levels in clinical populations, J. Clin. Endocrinol. Metab., 99(5):1631-7.
  • SOLLID S.T. (2016), Effects of vitamin D binding protein phenotypes and vitamin D supplementation on serum total 25(OH) D and directly measured free 25(OH)D, Eur. J. Endocrinol. April 1, 174:445-452.
  • TANGPRICHA V. (2015), Free 25-Hydroxyvitamin D Concentrations in Cystic Fibrosis, Am. J. Med. Sci. 2015 Nov;350(5):374-9. - ALOIA J. (2015), Free 25(OH)D and the Vitamin D Paradox in African Americans, J. Clin. Endocrinol. Metab. 2015 Jul 10:JC20152066.
  • VAN HOOFF H.J., Swinkels LM, Ross HA, Sweep CG, Benraad TJ. Determination of nonprotein-bound plasma 1,25-dihydroxyvitamin D by symmetric (rate) dialysis. Anal Biochem. 1998 May 1;258(2):176-83.
References to Summary

References to 25-OH-Vitamin-D

  • Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr. 2008 Apr;87 (4):1080S-6S
  • Hollis BW. Editorial: The determination of circulating 25-hydroxyvitamin D: no easy task. J Clin Endocrinol Metab. 2004 Jul;89 (7):3149-51
  • Lips P. Vitamin D physiology. Prog Biophys Mol Biol. 2006 Sep;92 (1):4-8
  • Macdonald HM, Mavroeidi A, Fraser WD, Darling AL, Black AJ, Aucott L, O'Neill F, Hart K, Berry JL, Lanham-New SA, Reid DM. Sunlight and dietary contributions to the seasonal vitamin D status of cohorts of healthy postmenopausal women living at northerly latitudes: a major cause for concern?. Osteoporos Int. 2011 Sep;22 (9):2461-72
  • Mavroeidi A, O'Neill F, Lee PA, Darling AL, Fraser WD, Berry JL, Lee WT, Reid DM, Lanham-New SA, Macdonald HM. Seasonal 25-hydroxyvitamin D changes in British postmenopausal women at 57 degrees N and 51 degrees N: a longitudinal study. J Steroid Biochem Mol Biol. 2010 Jul;121 (1-2):459-61
  • Snellman G, Melhus H, Gedeborg R, Byberg L, Berglund L, Wernroth L, Michaelsson K. Determining vitamin D status: a comparison between commercially available assays. PLoS One. 2010;5 (7):e11555
  • Tsur A, Metzger M, Dresner-Pollak R. Effect of different dress style on vitamin D level in healthy young Orthodox and ultra-Orthodox students in Israel. Osteoporos Int. 2011 Nov;22 (11):2895-8
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