| Vitamin D Replacement
| Osteomalacia-Rickets-Vitamin D
| Vitamin D resistant rickets
| Vitamin D (25 OH D) Testing
| X linked Hypophosphataemic rickets
Used to screen for Osteomalacia/Rickets. Vitamin D replacement is appropriate for deficiency < 30 nmol/L. Those with higher levels of treatment may be appropriate in some patients. There has been a change in guidance. Routine testing of Vitamin D should NOT be undertaken.
- Most assays measuring vitamin D test the biologically inactive form, 25-(OH)-Vitamin D, as it is the major form of vitamin D in circulation.
- The active metabolite, 1,25-OH-Vitamin D, has a circulating half-life of 4 to 6 hours, making it difficult to accurately interpret.
- Vitamin D deficiency is defined by a 25-(OH)-Vitamin D level < 20 ng/mL, and insufficiency as a level between 21 to 29 ng/mL.
- Normal vitamin D levels range from 30 to 100 ng/m
Do not measure 1,25(OH)D as it may be falsely normal or high, has a short half life and is a 1/1000 concentration as 25(OH)D and is less than useless. Measure 25(OH)D
When to check vitamin D level
- The patient has one or more of the following clinical features
- Widespread or localised bone pain and tenderness
- Children bone deformity, reluctance to weight bear, impaired growth
- Proximal muscle weakness, i.e. quadriceps and glutei. Difficulty rising from a chair or a waddling gait.
- Swelling, tenderness and redness at pseudo-fracture sites
- Fractures, typically femoral neck, scapula, pubic rami, ribs or vertebrae
- Non-specific myalgia, especially with a raised creatinine kinase (CK)
- Myalgia on the prescription of a statin
- And the patient has one or more of the following risk factors
- Black and ethnic minority patients with darker skin
- Elderly patients in residential care or housebound
- Intestinal malabsorption, for example cystic fibrosis, coeliac disease,
- Inflammatory bowel disease, gastrectomy or bariatric surgery, radiation enteritis
- Routine covering of face or body, for example wearing a veil or habitual sunscreen use
- Vegan or vegetarian diet, Liver or renal disease
- Medications including cholestyramine, rifampicin, glucocorticoids, antiretrovirals
- Pregnant and lactating women, Obesity (BMI >30)
- Check you have excluded other causes
- Myeloma, Rheumatoid arthritis
- Polymyalgia rheumatica, Hypothyroidism
- Other clinically appropriate indications for measuring vitamin D include
- Older patients with a history of falls
- Bone disease that may be improved with vitamin D treatment or where correcting vitamin D before treatment is appropriate
- Before commencing Zoledronic acid or Denosumab
- Unexplained high ALP, Low Phosphate or calcium or raised PTH
- Before thyroidectomy or bariatric surgery
- Anticonvulsant treatment (NICE guidelines recommend check every 2 - 5 years).
- At initial diagnosis in patients with multiple sclerosis
- Sample requirements
- If the patient is on high dose biotin therapy (>5 mg/day), collect the sample at least 8 hours after the last dose.
- Adults, blood taken into a 5mL gold top tube
- Interpretation of 25-Hydroxyvitamin D (vitamin D)
|Vitamin D nmol/L||Vitamin D status|
|> 50 || Adequate|
|30 - 50|| Insufficiency|
|< 30 ||Deficiency|