Evidence-based findings
High vitamin D levels, known as vitamin D toxicity (VDT) or hypervitaminosis D, causes several serious clinical manifestations:
Primary Clinical Symptoms
The most commonly observed symptoms of vitamin D toxicity include [1]:
- Confusion and apathy
- Recurrent vomiting
- Abdominal pain
- Polyuria (excessive urination)
- Polydipsia (excessive thirst)
- Dehydration
Key Laboratory Finding
Hypercalcemia is the hallmark clinical manifestation of vitamin D toxicity [1,4]. Serum 25-hydroxyvitamin D [25(OH)D] concentrations higher than 150 ng/ml (375 nmol/l) are characteristic of VDT due to vitamin D overdosing [1]. Some sources define VDT as serum 25(OH)D levels exceeding 100 ng/mL (250 nmol/L) [4].
Mechanism of Hypercalcemia
Vitamin D and its metabolites in excessive levels induce hypercalcemia through [4]:
- Elevation of osteoclastic bone resorption
- Increased calcium presence in renal tubules
- Enhanced intestinal calcium absorption (through increased calcium-binding protein production)
- Decreased parathyroid hormone synthesis
Kidney-Related Effects
Related evidence suggests that vitamin D excess can contribute to acute kidney injury (AKI) [3]. The relationship appears reciprocal, where both vitamin D toxicity can cause kidney problems and kidney injury can disrupt vitamin D homeostasis.
Established clinical knowledge
Based on standard clinical practice, vitamin D toxicity typically results from:
- Excessive long-term intake of high-dose vitamin D supplements
- Inadvertent overdosing with pharmacological vitamin D preparations
- Use of improperly formulated or unlicensed vitamin D products
Limitations
The available sources focus primarily on toxicity symptoms and mechanisms but provide limited information about specific treatment protocols, long-term outcomes, or recovery timelines from vitamin D toxicity.