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Vitamin D Deficiency

Vitamin D deficiency means the body lacks enough vitamin D to absorb calcium and keep bones strong. It is surprisingly common, often silent, and easily diagnosed with a blood test and corrected with supplements.

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Vitamin D deficiency occurs when the body does not have enough vitamin D to work properly. Vitamin D's central job is helping the intestines absorb calcium, which keeps bones strong; it also supports muscle and immune function. The skin makes vitamin D from sunlight, and small amounts come from food. Deficiency is one of the most common nutritional problems in adults — and it is common even in sunny St. Petersburg, because sunscreen, indoor lifestyles, and aging skin all limit how much vitamin D the body actually makes. 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.
More is not better: very high-dose supplementation without monitoring can cause elevated calcium levels and kidney problems, so extreme doses should be used only under medical supervision. 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.
Because deficiency is silent, it is usually caught during routine preventive care. The primary-care team at Zimmer Medical Group checks vitamin D when risk factors or bone health concerns warrant it and can build repletion into your overall bone-protection plan.

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