Diagnostic Use
There is no universally accepted definition of vitamin D sufficiency, with the most commonly recommended thresholds between 50 – 80 nmol/L. Such thresholds are usually stated without reference to the season of the year, but presumably refer to the lowest 25hydroxy vit D level during the year.
Interpretation
Minimum 25-OH vit D level (in nmol/L, by quarter of a year) required to maintain a predicted 25-OH vit D nadir >=50 nmol/L (considered sufficient) all year round – according to age and gender (abridged version only).
| Age |
18 – 50 YEARS |
18 – 50 YEARS |
50 – 65 YEARS |
50 – 65 YEARS |
> 65 YEARS |
> 65 YEARS |
| Month |
Women |
Men |
Women |
Men |
Women |
Men |
| Jan – Mar |
71 |
74 |
66 |
72 |
62 |
64 |
| April – Jun |
60 |
60 |
59 |
60 |
58 |
58 |
| July – Sep |
50 |
50 |
50 |
50 |
50 |
50 |
| Oct – Dec |
58 |
60 |
55 |
58 |
53 |
55 |
For details – must refer to Bolland MJ et al. The effects of seasonal variation of 25-hydroxyvitamin D on diagnosis of vit D insufficiency. NZMJ 2008; 121 (1286): 63-74
Reference Intervals
| VITAMIN D LEVEL (nmol/L) |
|
| <25 |
Vitamin D deficiency |
| 25 – 50 |
Vitamin D insufficiency |
| 50 – 250 |
Vitamin D sufficiency |
| >250 |
At risk of Vitamin D toxicity |
Generally vitamin D supplementation is recommended to individuals at high risk of vitamin D deficiency. Measurement of 25OHD levels is not routinely required before prescribing vitamin D supplements, or to monitor response to supplements. If 25OHD is measured, it is important to take account of seasonal variation: 25OHD levels are typically 10-30 nmol/L higher in late summer than in late winter.
Test Method
Principle: Competitive Immunoassay
Reagents: Siemens Atellica IM Vitamin D
Analyser: Siemens Atellica IM