What is the treatment for vitamin D toxicity?

Treatment for Vitamin D Toxicity

The primary treatment for vitamin D toxicity includes immediate discontinuation of all vitamin D supplements, increased fluid intake, restriction of dietary calcium, and in severe cases, administration of bisphosphonates and glucocorticoids. 1

Diagnosis and Assessment

Definition

• Vitamin D toxicity is defined by elevated 25-hydroxyvitamin D [25(OH)D] levels, typically:
  • Concerning: >100 ng/mL (250 nmol/L)
  • Toxic: >150 ng/mL (375 nmol/L) 1, 2

Laboratory Evaluation

• Serum calcium (typically elevated)
• Serum phosphorus (normal or high)
• Alkaline phosphatase (normal or low)
• Parathyroid hormone (suppressed)
• Renal function tests (creatinine, BUN)
• 24-hour urine calcium (elevated) 1, 2

Treatment Algorithm

Step 1: Immediate Interventions

• Discontinue all vitamin D supplements and identify the source of toxicity 1
• Increase oral fluid intake to promote calcium excretion 1
• Restrict dietary calcium intake temporarily 1

Step 2: Management Based on Severity

For Mild to Moderate Hypercalcemia (Ca <14 mg/dL):

• Oral hydration with increased fluid intake
• Low calcium and phosphorus diet
• Monitor serum calcium and vitamin D levels every 2-4 weeks 1, 2

For Severe Hypercalcemia (Ca ≥14 mg/dL):

1. Intravenous hydration with normal saline
2. Loop diuretics (after adequate hydration) to enhance calcium excretion
3. Consider glucocorticoids to decrease intestinal calcium absorption and vitamin D activity
4. Calcitonin for rapid but short-term reduction in calcium levels
5. Bisphosphonates for persistent hypercalcemia 1, 2

Monitoring and Follow-up

• Monitor serum calcium and 25(OH)D levels every 2-4 weeks initially
• Regularly assess renal function
• Be aware that vitamin D toxicity may take months to resolve due to the long half-life of vitamin D stored in adipose tissue 1
• Continue low calcium diet until normalization of serum calcium and vitamin D levels

Special Considerations

• Vitamin D toxicity can cause significant morbidity including:

  • Acute kidney injury
  • Neurological symptoms (confusion, altered mental status)
  • Gastrointestinal symptoms (nausea, vomiting, constipation)
  • Cardiovascular calcification (especially in patients with chronic kidney disease) 1, 3

• Common causes of vitamin D toxicity:

  • Excessive supplementation (doses >10,000 IU daily for prolonged periods)
  • Accidental overdose (single doses in the millions of IU)
  • Manufacturing errors in supplement production
  • Genetic factors affecting vitamin D metabolism (e.g., CYP24A1 mutations) 1, 4

Prevention

• Educate patients about safe vitamin D supplementation (generally not exceeding 4,000 IU daily for adults)
• Consider regular monitoring of vitamin D levels if supplementation is resumed
• Check serum 25(OH)D levels before initiating high-dose vitamin D therapy
• Monitor serum calcium and phosphorus every 3 months during high-dose supplementation 1

Remember that vitamin D toxicity effects may persist for months despite removal of the exogenous source due to storage in fat tissue 2. Treatment should be continued until normalization of both calcium and vitamin D levels.