1,25 dihydroxy Vitamin D (1,25-DHCC)
1,25 DHCC, 1,25VitD
1,25-dihydroxycholecalciferol (1,25-D), the active metabolite of
vitamin D is formed in the kidney
from 25-hydroxycholecalciferol(25-D). 1,25-D may also be
produced by other cells in some pathological conditions
Request on ICE
Analyzed by referral laboratory if specific criteria met.
1,25-dihydroxyvitamin D is the active metabolite of Vitamin
D. It is formed from 25-hydroxyvitamin D in the proximal
tubule of the kidney by the action of 1α hydroxylase. Levels
are tightly controlled and are regulated by PTH, phosphate, calcium
and 1, 25-dihydroxyvitamin D itself. Serum levels give a poor
indication of Vitamin D status in deficiency or excess and
25-hydroxyvitamin D should be measured in these
1,25-dihydroxyvitamin D can also be produced by extra renal
synthesis in sarcoidosis, lymphoma and granulomatous disorders.
The primary use of serum levels of 1, 25-dihydroxyvitamin D is
in the differential diagnosis of hypercalcaemia, renal disease,
secondary hyperparathyroidism, hypocalcaemia and in distinguishing
Vitamin D resistance syndromes from Vitamin D deficiency
No dietary or drug restrictions are required.
Serum in red top (plain) tube together with a SST sample for
Please contact laboratory before collection. Samples should be
transported to laboratory immediately.
Sent to the Royal Liverpool Hospital.
Causes for Rejection
Not meeting specific criteria for analysis. Delay in sample
Check the laboratory report.
- 1,25 di-hydroxy vitamin D:
- 43-144 pmol/L
- 25-hydroxy vitamin D:
- <= 15 nmol/L : indicative of severe Vitamin D
- 16 - 30 nmol/L: indicative of Vitamin D deficiency
- 31 - 50 nmol/L: indicative of Vitamin D insufficiency
- > 51 nmol/L : indicative of adequate
Vitamin D status
- > 150 nmol/L : may indicate Vitamin D
Levels may be up to 20% higher in children due to the effects of
In type 1 (deficient 1 alpha-hydroxylase) inherited rickets
1,25-D is low and in type 2 (end-organ resistance) 1,25-D may be
high. 1,25-D may also be elevated in hereditary hypophosphataemic
rickets with hypercalcuria. 25-D is usually normal in all