What are the effects of excessive vitamin D (Vitamin D) intake?

From the Guidelines

Excessive vitamin D intake can lead to vitamin D toxicity, causing elevated calcium levels in the blood, which can result in severe health complications, including kidney failure and death. The effects of excessive vitamin D intake are mediated by high calcium levels and include hypercalcemia, hypercalciuria, dizziness, and renal failure 1. Vitamin D toxicity symptoms occur due to the increased intestinal calcium absorption and bone resorption, releasing more calcium into the bloodstream than the kidneys can eliminate.

Key Points to Consider

• Vitamin D toxicity is rare but can occur with true over-doses, deliberate or accidental, typically single doses of millions IU or daily doses of >10,000 or even 100,000 IU 1.
• The safety limit for serum 25(OH)D levels is considered to be 100 ng/mL, although most international authorities consider a vitamin D intake of 2,000 IU daily as absolutely safe 1.
• Hypercalcemia caused by excess vitamin D in generally healthy adults has been observed only if daily intake was > 100,000 IU or if the 25(OH)D level exceeded 100 ng/mL 1.
• Treatment for vitamin D toxicity involves stopping vitamin D supplements, limiting dietary calcium, increasing fluid intake, and in severe cases, medications like bisphosphonates or corticosteroids to reduce calcium levels.

Recommendations

• Most people should not exceed 4,000 IU of vitamin D daily unless prescribed by a healthcare provider.
• If you experience symptoms of vitamin D toxicity, such as nausea, vomiting, weakness, frequent urination, kidney problems, bone pain, and calcium deposits in soft tissues, seek medical attention immediately.
• It is essential to maintain a minimum level of vitamin D in all seasons, taking into account seasonal variation, and to monitor serum 25(OH)D levels to avoid toxicity 1.

From the Research

Effects of Excessive Vitamin D Intake

Excessive vitamin D intake can lead to a range of health problems, including:

• Hypercalcemia (elevated calcium levels in the blood) 2, 3, 4, 5, 6
• Acute kidney injury 3, 4, 5
• Nausea and vomiting 3, 4, 6
• Muscle weakness 3
• Fatigue 5
• Gastrointestinal complaints 5
• Lethargy 6
• Hypotonia (low muscle tone) 6
• Constipation 6
• Polyuria (excessive urine production) 6
• Leucocyturia (excessive white blood cells in the urine) 6

Diagnosis and Treatment

Diagnosis of vitamin D intoxication is typically made based on symptoms, physical examination, and laboratory tests, including:

• Serum calcium levels 2, 3, 4, 5, 6
• Serum phosphorus levels 2
• Serum 25-hydroxyvitamin D levels 2, 3, 5
• Parathyroid hormone (PTH) levels 2
• Urine calcium/creatinine ratio 2 Treatment for vitamin D intoxication typically involves:
• Discontinuation of vitamin D intake 2, 3, 4, 5, 6
• Hyperhydration 2, 3, 4, 5, 6
• Loop diuretics 2, 4, 5, 6
• Glucocorticoids 2
• Calcitonin 2, 4, 5
• Bisphosphonates 2, 5, 6

Prevention

Prevention of vitamin D intoxication is crucial, and can be achieved by:

• Monitoring serum vitamin D levels regularly 2, 3
• Avoiding excessive vitamin D intake 2, 3, 4, 5, 6
• Being aware of the potential dangers of vitamin D overdose 3
• Considering the use of dietary supplements as a potential source of toxicity 5