Serum concentration of 25-OH D (total vitamin D) is considered to be the most reliable measure of overall vitamin D status and thus can be used to determine whether a patient is Vitamin D deficient. Assessment of Vitamin D status may be required to determine the cause of abnormal serum calcium concentrations in patients.
Vitamin D exerts an affect primarily on calcium metabolism. Calcitriol upregulates absorption of calcium and phosphate form the gut and the reabsorption of calcium in the renal tubules. If adequate levels of vitamin D are not maintained or if demand exceeds supply then vitamin D deficiency can occur, resulting in less available calcium for bone mineralisation. Reduced bone mineral density is a feature if osteoporosis; severe vitamin D deficiency can cause rickets in children and osteomalacia in adults. Vitamin D receptors have been found on many different cell and tissue types, suggesting the involvement of vitamin D with immunological, cardiovascular disease and cancer, however there is not yet sufficient evidence to justify its measurement in these situations.
The reference range reported at James Cook University Hospital are taken from the study Systemic Reviews, Meta analyses and Clinical Guidelines Published Within the Last 10 Years. Pearce S, Cheatham T, BMJ vol: 340, Jan 2010 pp142- 147.
- <25 nmol/L – DEFICIENT
- 25-50 nmol/L – INSUFFICIENT
- 50-75 nmol/L – ADEQUATE
- >75 nmol/L – OPTIMUM