What are the symptoms of vitamin D toxicity?

Symptoms of Vitamin D Toxicity

Vitamin D toxicity is primarily characterized by hypercalcemia, hypercalciuria, dizziness, and renal failure, and typically occurs with serum 25(OH)D levels above 150 ng/mL. 1, 2

Clinical Manifestations of Vitamin D Toxicity

Vitamin D toxicity results from excessive intake of vitamin D supplements, usually through prescription errors, manufacturing errors, or self-medication with mega-doses. The symptoms are primarily related to hypercalcemia and its duration.

Common Symptoms

• Gastrointestinal symptoms:

  • Nausea and vomiting
  • Constipation
  • Abdominal pain
  • Anorexia
  • Weight loss

• Neurological symptoms:

  • Altered mental status/confusion
  • Dizziness
  • Fatigue
  • Headache

• Renal manifestations:

  • Polyuria
  • Polydipsia
  • Acute kidney injury
  • Kidney stones

• Cardiovascular effects:

  • Hypertension
  • Cardiac arrhythmias
  • Accelerated cardiovascular calcification 1

• Other symptoms:

  • Pancreatitis 3, 4
  • Bone pain
  • Muscle weakness

Laboratory Findings in Vitamin D Toxicity

Characteristic laboratory abnormalities include:

• Elevated serum 25(OH)D levels (typically >150 ng/mL)
• Hypercalcemia (serum calcium >10.5 mg/dL)
• Hyperphosphatemia
• Suppressed parathyroid hormone (PTH) levels
• Hypercalciuria
• Elevated BUN and creatinine (in cases of acute kidney injury) 1, 2

Risk Factors for Vitamin D Toxicity

Vitamin D toxicity is rare but can occur with:

• Prescription errors (mega-doses of vitamin D)
• Manufacturing errors in supplements 5
• Self-medication with excessive doses
• Prolonged intake of doses >10,000 IU daily 1
• Individual variation in vitamin D metabolism 1

Important Considerations

• Vitamin D toxicity is rarely seen with normal supplementation but has been reported more frequently in recent years due to increased vitamin D supplement use 2
• Toxicity typically occurs with 25(OH)D levels above 150 ng/mL, though cardiovascular risks may begin at levels above 100 ng/mL 1, 2
• Effects of toxicity may persist for months after discontinuation due to vitamin D storage in fat tissue 2
• Case reports document toxicity from cumulative doses as high as 2,400,000 IU over just 4 days 6 and 6,360,000 IU over longer periods 3

Prevention of Vitamin D Toxicity

• Avoid doses exceeding 4,000 IU daily (the upper limit of safety recommended by NIH) 1
• Monitor serum calcium and phosphorus levels every 3 months during high-dose supplementation 1
• Ensure proper dosing instructions for vitamin D supplements, especially with imported medications 6
• Recheck 25(OH)D levels after 3-6 months of supplementation 1

Vitamin D toxicity is a serious condition that requires prompt recognition and treatment to prevent complications. The symptoms primarily result from hypercalcemia and can affect multiple organ systems, with potential long-term consequences if not addressed quickly.