Overview #
Serum 25-OH D3 levels (1):
| Severity (1) | Nanomol/L |
| MILD | 30-49 |
| MODERATE | 12.5-29 |
| SEVERE | < 12.5 |
- Indications for testing:
- (see section on risk factors)
- MBS criteria for billing https://www.nps.org.au/radar/articles/mbs-item-number-changes-for-vitamin-b12-folate-and-vitamin-d-tests
- No indication to check vitamin D levels in low risk, healthy individuals (1)
- Note that the Vitamin D biochemistry request assesses for the pre-cursor form of vitamin D (25-OH cholecalciferol, see diagram in physiology), hence would not reflect activity if the patient is receiving calcitriol therapy.
- More relevant for subacute settings (geriatrics/ rehab/ GP) vs acute inpatient
- Important to treat if:
- Moderate/ severe deficiency (see Ix section)
- Symptomatic
- Before starting osteoporosis treatment e.g. Denosumab injections (have to be calcium + vitamin D replete)
Triage #
Non-urgent – attend by end of your shift and/or clarify during morning ward round
Risk factors #
Intrinsic factors (1)
- Elderly – malnutrition
- Impaired absorption or conversion of vitamin D precursors – liver, renal, GIT, hypoparathyroidism
- People with a dark skin tone
Extrinsic factors (1)
- Reduced sunlight exposure e.g. housebound, reduced mobility
Clinical features #
- Most often asymptomatic
- Otherwise mild bone pain, muscle weakness, progressing to osteomalacia/ osteoporosis if severe
- Osteoporosis can present as minimal trauma fracture e.g. post-fall from standing height
Investigations #
Serum 25-OH D3 interpretation (1):
| Severity (1) | Nanomol/L |
| MILD | 30-49 |
| MODERATE | 12.5-29 |
| SEVERE | < 12.5 |
- 25-OH levels (instead of activated vitamin D) are associated with fracture risk, and reflect total body stores (3)
- Note that the precursor form of vitamin D (25-OH) is irrelevant in patients with chronic renal impairment, and the activated form would have to be requested specifically
Other Ix:
- Calcium
- Hypocalcaemia has to be corrected before starting denosumab therapy (4)
- Ca/Mg/PO4 as part of nutrition screen, refeeding protocol
- PTH
- If Ca2+ levels are abnormal, to identify hyper/hypoparathyroidism
Management #
| 1st line | If mild: Consider lifestyle modification e.g. sunlight exposure If from nursing home or housebound, or osteoporosis/ high falls risk: Colecalciferol 25-50 microg PO daily while inpatient, then 25 microg PO daily on discharge 25 microg = 1000 international unitsContraindications: hypercalcaemia, caution if hyperphosphataemia, if on calcitriol/ other over-the-counter vitamin D products (5) If moderate – severe:Colecalciferol 50 microg PO BD daily while inpatient, then 50 microg PO daily on discharge To consider higher doses of cholecalciferol if (1):High BMI Drugs affecting liver metabolism e.g. RifampicinFat malabsorption e.g. cystic fibrosis, IBD If factors below apply, then 2nd line Mx, to consult endocrine team (6):mod- severe renal impairment e.g. requiring dialysis hypocalcaemia in hypoparathyroidismhypophosphataemic rickets |
| 2nd line | Calcitriol 0.25 microg PO daily, then increase by 0.25 microg every 2-4 weeks, aiming for 0.5-1 microg PO daily (6)Monitor serum Ca2+ at baseline, then twice during first week, then 2-4 weeks, then every 2-3 months |
Follow-up
- GP to recheck Vitamin D levels in 4-6 weeks post d/c, if levels are replete
- But not if patient is on calcitriol (would need Ix with activated vitamin D)
- Aim to reduce to 25microg daily/ 1000 international units
Monitor for complications e.g. hyper Ca2+ – nausea, vomiting, constipation, muscle weakness (5), and withhold/cease if necessary
References #
- eTG Complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2021. Vitamin D deficiency [updated 2019 Jun; cited 2021 Aug 20]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=vitamin-d-deficiency&guidelineName=Bone%20and%20Metabolism&topicNavigation=navigateTopic#toc_d1e209
- Costanzo L. Physiology. 4th ed. Philadelphia: Saunders, Inc; 2010.
- Glendenning P. Measuring Vitamin D [Internet]. NPS Medicinewise. 2021 [cited 16 September 2021]. Available from: https://www.nps.org.au/australian-prescriber/articles/measuring-vitamin-d
- Australian medicines handbook online [Internet]. Adelaide (S.Australia): Australian Medicines Handbook Pty Ltd; 2000. Denosumab; [updated 2021 Jul; cited 2021 Sept 16]. Available from: https://amhonline.amh.net.au.acs.hcn.com.au/chapters/endocrine-drugs/drugs-affecting-bone/other-drugs-affecting-bone/denosumab?menu=vertical
- Australian medicines handbook online [Internet]. Adelaide (S.Australia): Australian Medicines Handbook Pty Ltd; 2000. Vitamin D; [updated 2021 Jul; cited 2021 Aug 20]. Available from: https://amhonline.amh.net.au.acs.hcn.com.au/chapters/endocrine-drugs/drugs-affecting-bone/vitamin-d?menu=vertical
- Australian medicines handbook online [Internet]. Adelaide (S.Australia): Australian Medicines Handbook Pty Ltd; 2000. Calcitriol; [updated 2021 Jul; cited 2021 Aug 20]. Available from: https://amhonline.amh.net.au.acs.hcn.com.au/chapters/endocrine-drugs/drugs-affecting-bone/vitamin-d/calcitriol?menu=vertical
Contributors
Reviewing Consultant/Senior Registrar
Dr Dolly Png
Dr Rahul Barmanray
