From the Guidelines
Vitamin D toxicity, also known as hypervitaminosis D, occurs when excessive amounts of vitamin D build up in the body, typically from supplement overuse rather than sun exposure or diet, and can lead to hypercalcemia, hyperphosphatemia, suppressed parathyroid hormone, and hypercalciuria, as noted in a study published in the Annals of Internal Medicine 1. The primary mechanism involves elevated calcium levels in the blood, which can lead to calcium deposits in soft tissues. Common symptoms include:
- Nausea
- Vomiting
- Weakness
- Frequent urination
- Kidney problems
- Bone pain
- Confusion Severe cases may cause kidney stones, kidney failure, heart rhythm abnormalities, and even death if left untreated. Toxicity usually develops with prolonged daily intake exceeding 10,000 IU, though the exact threshold varies between individuals, and the 25-(OH)D level associated with toxicity is often defined as >500 nmol/L [>200 ng/mL] 1. If you suspect vitamin D toxicity, stop taking supplements immediately and seek medical attention, as treatment typically involves discontinuing vitamin D supplements, limiting dietary calcium, increasing fluid intake, and in severe cases, medications to lower blood calcium levels, and most people recover fully when the excess vitamin D is cleared from the body. It is essential to note that the role of 25(OH)D deficiency and its correction in patients on maintenance dialysis therapy is controversial, and the required daily vitamin D intake for patients of any age with CKD is unknown 1. However, the recommended daily allowance for vitamin D in individuals over 60 years is 800 IU, and for younger adults 400 IU, and the safer vitamin D sterol may be ergocalciferol rather than cholecalciferol 1.
From the Research
Symptoms of Vitamin D Toxicity
The symptoms of vitamin D toxicity can be severe and include:
- Confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration 2
- Vomiting, dehydration, pain, and loss of appetite 3 These symptoms can occur due to excessive long-term intake of vitamin D, malfunctions of the vitamin D metabolic pathway, or the existence of coincident disease that produces the active vitamin D metabolite locally 2.
Causes of Vitamin D Toxicity
Vitamin D toxicity can be caused by:
- Exogenous factors such as inadvertent or improper intake of extremely high doses of pharmacological preparations of vitamin D 2
- Endogenous factors such as excessive production of an active vitamin D metabolite in granulomatous disorders and in some lymphomas or reduced degradation of that metabolite in idiopathic infantile hypercalcemia 2
- Manufacturing errors, overdosing by patients or prescribers, and combinations of these factors 3
- Loss of function mutation in cytochrome P450 (CYP)24A1, a key enzyme involved in the degradation of 25(OH)D and 1,25(OH)2D into inactive metabolites 4
Diagnosis and Management
Diagnosis of vitamin D toxicity can be made by measuring serum 25-hydroxyvitamin D [25(OH)D] concentrations, which are typically higher than 150 ng/ml (375 nmol/l) in cases of vitamin D overdosing 2. Management of vitamin D toxicity requires prompt identification and treatment to prevent serious health effects 2, 5.