Vitamin D Deficiency
Vitamin D deficiency occurs when the body does not get or produce enough vitamin D, a fat-soluble vitamin essential for calcium absorption, bone health, immune function, and mood regulation. Vitamin D is unique because the body can produce it through skin exposure to sunlight, yet deficiency is remarkably common worldwide due to limited sun exposure, dietary insufficiency, and certain medical conditions. Prolonged vitamin D deficiency can lead to bone disorders such as rickets in children and osteomalacia or osteoporosis in adults.
Symptoms
Causes
- Inadequate sun exposure due to indoor lifestyle, sunscreen use, or living at high latitudes
- Insufficient dietary intake of vitamin D-rich foods
- Malabsorption conditions such as celiac disease, Crohn's disease, or cystic fibrosis
- Obesity, which sequesters vitamin D in fat tissue and reduces its bioavailability
- Kidney or liver disease impairing vitamin D conversion to its active form
Risk Factors
- Dark skin pigmentation (melanin reduces vitamin D synthesis)
- Living at northern latitudes (above 37°N) with limited winter sunlight
- Older age (decreased skin synthesis capacity)
- Exclusively breastfed infants without vitamin D supplementation
- Obesity (BMI ≥ 30)
- Housebound or institutionalized individuals
- Wearing clothing that covers most of the skin
Diagnosis
- Serum 25-hydroxyvitamin D (25(OH)D) blood test — the standard measure
- Parathyroid hormone (PTH) level, which rises in response to low vitamin D
- Serum calcium and phosphorus levels
- Bone density scan (DEXA) if osteoporosis is suspected
Treatment
- Vitamin D3 (cholecalciferol) supplementation at doses tailored to the degree of deficiency
- High-dose loading therapy (50,000 IU weekly for 8-12 weeks) for severe deficiency
- Maintenance supplementation of 1,000-2,000 IU daily after levels normalize
- Increasing dietary intake of vitamin D-rich foods (fatty fish, egg yolks, fortified milk and cereals)
- Safe sun exposure (10-30 minutes of midday sun several times per week)
- Treatment of underlying malabsorption conditions
Prevention
- Get regular, moderate sun exposure (10-30 minutes several times per week, depending on skin type)
- Consume vitamin D-rich foods including salmon, sardines, egg yolks, and fortified products
- Take a daily vitamin D supplement, especially during winter months
- Ensure breastfed infants receive 400 IU of vitamin D daily
- Have vitamin D levels checked periodically, especially if at high risk
When to See a Doctor
- You experience persistent bone or muscle pain with fatigue
- You have risk factors for deficiency and want to have your levels tested
- You have a condition that impairs vitamin D absorption or metabolism
Frequently Asked Questions
Related Conditions
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