Season : Reduced exposure to UV radiation October-April
Latitude : Reduced exposure to UV radiation
Sunblock use : Reduced exposure to UV radiation
Clothing : Reduced exposure to UV radiation
Institutionalization : Reduced exposure to UV radiation
Skin pigmentation : Absorption of UV radiation by melanin
Malabsorption : e.g. pancreatic insufficiency, inflammatory bowel disease, coeliac disease, bariatric surgery, medications such as cholestyramine and orlistat
Obesity : Sequestration of Vitamin D in fat
Drugs : Induced metabolism of Vitamin D to inactive calcitroic acid e.g. rifampicin, phenytoin, glucocorticoids, HAART for HIV, transplant medications
Severe liver failure : Failure to 25-hydroxylate vitamin D
Nephrotic syndrome : Loss of Vitamin D in urine
Chronic kidney disease : Hyperphosphataemia suppresses 1-hydroxylation
|
Interpretation |
25 hydroxy vitamin D Level (nmol/L) CX SMH |
Action |
|
|
Deficiency |
<40 <25 |
Replace vitamin D: prescribe loading dose |
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|
Insufficiency |
40-69 25-50 |
Consider referral to secondary care and vitamin D replacement if:
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|
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‘Replete’ |
70-150 >50 |
Does not need replacement or continue present replacement dose. |
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Possibly toxic |
>150 |
Check calcium: needs to be referred to hospital if hypercalcaemic. Consider referring sample to different laboratory as there may be sample interference. |
Loading dose over 3 months:
Prescribe colecalciferol (Dekristol) 20,000 IU capsules, one capsule weekly for 12 weeks, then go on to maintenance dose. Consider giving IM ergocalciferol 300,000 IU two injections spaced by 3 months if there are concerns regarding absorption (e.g. in malabsorption). Maintenance dose: Usually between 1000-2000 IU colecalciferol per day depending on weight, e.g. Holland and Barrett Vitamin D3 25 microgram tablets, 1-2 tablets a day, or colecalciferol (Dekristol) 20,000 IU capsules, one capsule every 2 weeks. Higher doses may be required e.g. if the patient is taking drugs that accelerate Vitamin D metabolism or if there are concerns regarding absorption. Maintenance should be continued so long as risk factors for Vitamin D deficiency are present. Notes on dosing:
Note: If the patient is hypercalcaemic they should be referred to the local Endocrinology service for further evaluation.
This guideline advocates the use of D3 or D2 for supplementation, not ‘active vitamin D’ (e.g. alfacalcidol, calcitriol) as the latter are more prone to the side effect of hypercalcaemia.
D3 is generally preferred as D2 may be less potent than D3, unit for unit. If the patient is being given supplementation for osteoporosis and osteopenia, they should also receive 1000 mg of supplemental calcium daily, as calcium and vitamin D supplementation is effective in reducing the risk of hip fracture. Vitamin D alone is not effective in reducing hip fractures. Calcium supplements alone appear to be associated with a higher risk of heart attack and stroke and are therefore not recommended. Pregnant and lactating women should be given calcium and 400 IU Vitamin D daily. Up to 10000 IU per day is not toxic when given for up to 5 months. Monitoring: Measure 25-hydroxyvitamin D, PTH, calcium after 3 months and 6-monthly thereafter to ensure that hypercalcaemia does not occur. Aim for 25-hydroxyvitamin D 'replete' level, with calcium and PTH levels within reference ranges. If in doubt, please refer to secondary care for advice. Stop the supplementation if hypercalcaemia or kidney stones occur or if 25 hydroxyvitamin D level is above the replete reference range. Prices of vitamin D:Vitamin D costs 2014
| Prescribable Options (for reference)
Calcium & D3 supplements
Ergocalciferol (D2)
Colecalciferol (D3)
Over the Counter Options (for reference) Printable vitamin D patient information sheet
There are many more OTC options than those listed. This list is not considered an endorsement of the specific supplements cited but purely reflects the fact that these are generally available locally from pharmacists and health food shops.
Cod liver oil capsules typically contain 200 IU per capsule but contain too much Vitamin A to be used as the sole source of vitamin D.
Similarly multivitamins generally contain too little vitamin D in relation to other vitamins to be used as the sole source of vitamin D.
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