From the Guidelines
Vitamin D overdose, also known as vitamin D toxicity or hypervitaminosis D, is a rare but potential harm of treatment with oral vitamin D, which may lead to hypercalcemia, hyperphosphatemia, suppressed parathyroid hormone, and hypercalciuria, as reported in studies such as 1 and 1.
Definition and Causes
Vitamin D toxicity typically occurs when taking more than 10,000 IU daily for extended periods, though toxicity usually requires doses exceeding 50,000 IU daily for several weeks or months. Symptoms include nausea, vomiting, weakness, frequent urination, kidney problems, bone pain, and confusion.
Diagnosis and Treatment
The main concern is elevated calcium levels in the blood (hypercalcemia), which can lead to serious complications including kidney damage. If you suspect vitamin D toxicity, stop taking supplements immediately and seek medical attention. Treatment involves discontinuing vitamin D, limiting dietary calcium, increasing fluid intake, and in severe cases, medications like bisphosphonates or corticosteroids to lower blood calcium, as suggested in studies such as 1 and 1.
Prevention
Most people should limit vitamin D supplementation to 600-2000 IU daily unless prescribed higher doses by a healthcare provider. Vitamin D toxicity doesn't occur from sun exposure or food sources, as the body regulates production and absorption from these natural sources. It is essential to be aware of the potential harms of screening and treatment, including misclassification of persons with a vitamin D deficiency, overdiagnosis, or underdiagnosis, as discussed in studies such as 1.
From the Research
Symptoms of Vitamin D Overdose
- Confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration are common clinical symptoms of vitamin D toxicity (VDT) or hypervitaminosis D 2
- Hypercalcemia, normal or high serum phosphorus levels, normal or low levels of alkaline phosphatase (ALP), high levels of serum 25OHD, low serum parathyroid hormone (PTH), and high urine calcium/creatinine are usually present in patients with VDI 3
- Severe hypercalcemia, acute kidney injury, and gastrointestinal bleeding can occur due to excessive vitamin D supplementation 4
Diagnosis and Treatment of Vitamin D Overdose
- Serum 25OHD levels above 150 ng/ml are considered as VDI 3, 2
- The main goal of treatment for VDI is correction of the hypercalcemia, which may include discontinuation of intake, a diet with low calcium and phosphorus content, intravenous hydration with saline, loop diuretics, glucocorticoids, calcitonin, and bisphosphonates 3, 5
- Emergency intervention is necessary when the calcium concentration exceeds 14 mg/dl due to the adverse effects of hypercalcemia on cardiac, central nervous system, renal, and gastrointestinal functions 3
Risks and Complications of Vitamin D Overdose
- Long-term vitamin D supplementation can result in increased risks of hypercalcemia and hypercalciuria, which are not dose related 6
- Vitamin D supplementation did not increase the risk of kidney stones in a systematic review and meta-analysis of 48 studies with 19,833 participants 6
- Excessive vitamin D supplementation may lead to significant clinical complications, including severe hypercalcemia, acute kidney injury, and gastrointestinal bleeding 4