Vitamin D Deficiency
NICE CKS Vitamin D deficiency in adults. Last revised Jan 2022
NICE Public Health Guideline [PH56] Vitamin D: supplement use in specific population groups. Last updated Aug 2017
Background Information
Definition
Vitamin D: a fat-soluble vitamin that acts primarily to increase calcium and phosphorus absorption from the bowel.
Active form: 1,25-dihydroxyvitamin D
Causes and Risk Factors
In the UK, 80-90% of vitamin D is derived from skin exposure to sunlight, 10-20% is derived from diet.
Causes of vitamin D deficiency
- Inadequate sun (UVB) exposure
- Intestinal malabsorption (e.g. Coeliac disease, Crohn's disease, cystic fibrosis)
- Severe liver failure
- End-stage chronic kidney disease
- Hereditary vitamin D-deficiency rickets
- Drugs (orlistat, antiepileptic drugs, etc.)
Risk factors
- ≥65 y/o
- Low / no exposure to sun
- Darker skin pigmentation
- Pregnant / breastfeeding
- Obese (BMI >30)
Diagnosis Guidelines
Testing for Vitamin D Deficiency
Do not routinely test for vitamin D deficiency in asymptomatic patients.
- Asymptomatic patient at higher risk of vitamin D deficiency does NOT need testing
- Patients being treated with antiresorptive agent and vitamin D supplements does NOT need testing
Test of choice: serum 25-hydroxyvitamin D
Indications for checking vitamin D level:
- Symptomatic
- Suspected bone disease that may improve with vitamin D treatment
- Bone disease that requires vitamin D deficiency correction prior treatment
Serum 25-hydroxyvitamin D is the best indicator of vitamin D deficiency, as it has a longer half-life (~2-3 weeks) and is the major circulating form of vitamin D.
Although 1,25-dihydroxyvitamin D is the active hormone form, it has a short half-life (~4-6 hours). Its level may remain normal or elevated even in vitamin D deficiency, due to secondary hyperparathyroidism increasing conversion.
Management Guidelines
Management
Lifestyle advice:
- Safe sunlight exposure
- Dietary advice on vitamin D and calcium intake
Oral vitamin D3 treatment:
- For rapid correction → loading dose (total of 300,000 IU over 6-10 weeks) followed by maintenance therapy (800-2,000 IU daily)
- For non-urgent correction → maintenance therapy (800-2,000 IU daily)
Assess need for calcium supplementation:
- If there is dietary insufficiency → advise to increase dietary calcium intake
- If dietary change not appropriate → calcium supplementation
NICE CKS states to seek specialist advice / arrange referral before starting vitamin D treatment in the following conditions.
Note: combination calcium and vitamin D preparations (such as Calcichew D3®) are not recommended for people needing high-dose vitamin D treatment, as they contain very low levels of vitamin D (200–400 IU per tablet) and may increase the risk of hypercalcaemia.
Prevention
Lifestyle advice:
- Safe sunlight exposure
- Dietary advice on vitamin D and calcium intake
Consider vitamin D supplement 400 IU daily in:
- ≥65 y/o with risk factors for vitamin D deficiency
- All other adults, particularly in autumn and winter
References
Original Guideline