Causes and Risk Factors
Vitamin D deficiency develops when the skin makes too little, the diet supplies too little, or the body cannot absorb or process what it gets:- Limited sun exposure: Working indoors, covering the skin, and consistent sunscreen use reduce production.
- Older age: Aging skin produces vitamin D less efficiently, and the kidneys activate it less well.
- Darker skin: Melanin reduces the skin's vitamin D production from the same amount of sun.
- Malabsorption: Digestive conditions such as celiac disease and Crohn's disease, and prior gastric bypass surgery, impair absorption of this fat-soluble vitamin.
- Obesity: Vitamin D is sequestered in fat tissue, lowering blood levels.
- Limited dietary intake: Very few foods naturally contain vitamin D, so diets low in fish, eggs, and fortified dairy supply little.
- Kidney or liver disease and certain medications: Both organs help activate vitamin D, and some seizure and steroid medicines speed its breakdown.
Symptoms
Most people with vitamin D deficiency feel nothing at all, which is why it is usually discovered on a blood test. When deficiency is significant or prolonged, it can cause:- Bone pain and tenderness: Severe deficiency softens bone — rickets in children and osteomalacia in adults.
- Muscle weakness and aches: Particularly in the hips and thighs, sometimes contributing to falls in older adults.
- Fatigue: Nonspecific, but frequently reported.
- Bone thinning over time: Chronic deficiency contributes to osteopenia and osteoporosis and raises fracture risk.
Diagnosis
A simple blood test measuring 25-hydroxyvitamin D confirms the diagnosis. Levels below 20 ng/mL are generally considered deficient, while 20 to 30 ng/mL is often called insufficient. Routine screening of healthy adults without risk factors is not generally recommended; testing is targeted to people with risk factors, bone disease, unexplained muscle symptoms, or malabsorption, and calcium and parathyroid hormone levels are sometimes checked alongside.Treatment
Treatment is safe, inexpensive, and effective:- Supplementation: Over-the-counter vitamin D3 (cholecalciferol) taken daily is the mainstay; significant deficiency is often treated first with several weeks of higher prescription-strength dosing, then a maintenance dose.
- Dietary sources: Fatty fish, egg yolks, and fortified milk and cereals contribute modest amounts.
- Sensible sun exposure: Brief, regular time outdoors helps, balanced against skin cancer risk — an important consideration in Florida.
- Treating the underlying cause: Malabsorption and kidney disease require tailored management, and levels are rechecked after about three months to confirm correction.
Complications
Because vitamin D governs how much calcium the body can absorb, prolonged deficiency has consequences well beyond a low lab value:- Osteomalacia: Softening of adult bone that causes deep, aching bone pain, tenderness over the ribs and hips, and in advanced cases small stress fractures.
- Secondary hyperparathyroidism: When calcium absorption falls, the parathyroid glands work harder and draw calcium out of the skeleton, a pattern that overlaps with hyperparathyroidism and accelerates bone loss.
- Falls and fractures: Weakness in the hip and thigh muscles combined with thinner bone raises fracture risk, a particular concern for older adults living independently.
- Rickets in children: Severe deficiency during growth causes bowed legs, delayed milestones, and skeletal deformity — uncommon today, but still seen.