What causes vitamin D toxicity?

From the Guidelines

Vitamin D toxicity is primarily caused by excessive intake of vitamin D supplements, not from sun exposure or food sources, and a level of 113 ng/mL is well above the recommended range and may lead to hypercalcemia, hyperphosphatemia, and other complications. This condition, also called hypervitaminosis D, typically occurs when someone takes very high doses of vitamin D supplements (usually exceeding 10,000 IU daily) for prolonged periods 1. The body cannot regulate vitamin D that comes from supplements as effectively as it regulates vitamin D produced in the skin from sunlight. When too much vitamin D is consumed, calcium absorption increases dramatically, leading to hypercalcemia (elevated blood calcium levels). This excess calcium can deposit in soft tissues, damage kidneys, and cause symptoms like nausea, vomiting, weakness, frequent urination, kidney stones, and in severe cases, kidney failure and abnormal heart rhythms.

Some key points to consider:

• The 25-(OH)D level associated with toxicity is often defined as >500 nmol/L [>200 ng/mL] 1.
• Treatment with vitamin D plus calcium may also be associated with increased risk for kidney stones; vitamin D alone does not seem to increase this risk 1.
• People with certain medical conditions like sarcoidosis or hyperparathyroidism are at higher risk 1.
• To avoid vitamin D toxicity, don't exceed recommended dosages (typically 600-800 IU daily for adults) unless specifically prescribed by a healthcare provider, and be cautious with multiple supplements that might contain vitamin D 1.
• A safe upper limit for serum 25(OH)D levels is considered to be 100 ng/mL, and levels above 50 ng/mL may not result in additional benefits than 30-44 ng/mL 1.

It's essential to note that the provided level of 113 ng/mL is above the recommended range and may lead to complications. Therefore, it is crucial to monitor vitamin D levels and adjust supplementation accordingly to avoid toxicity.

From the Research

Causes of Vitamin D Toxicity

• Vitamin D toxicity can be caused by very high doses of vitamin D, mostly due to erroneous prescription or administration of vitamin D, and less commonly, contaminated foods or manufacturing errors of vitamin D-containing supplements 2.
• The use of dietary supplements, such as creatine and protein supplements, can also be a potential source of toxicity, even if the product label does not claim to contain vitamin D 2.
• 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 can also lead to vitamin D toxicity 3.
• Vitamin D toxicity can also be caused by increased bone resorption, which can be treated with bisphosphonates such as pamidronate 4.

Risk Factors for Vitamin D Toxicity

• Receiving multiple intramuscular injections of vitamin D3, with a median cumulative dose of 4,200,000 IU, can increase the risk of vitamin D toxicity 5.
• Reduced baseline levels of renal function can also increase the risk of vitamin D toxicity, particularly in patients with osteoporosis or osteomalacia 6.
• Increased public awareness of vitamin D-related health benefits may increase the risk of vitamin D toxicity due to self-administration of vitamin D in doses higher than recommended for age and body weight 3.

Clinical Manifestations of Vitamin D Toxicity

• Clinical manifestations of vitamin D toxicity can include gastrointestinal symptoms, polyuria/polydipsia, altered sensorium, pancreatitis, acute kidney injury, and nephrocalcinosis 5.
• Hypercalcemia, with a median total serum calcium level of 13.95 mg/dl, and elevated 25-hydroxyvitamin D levels, with a median level of 306 ng/ml, are common laboratory findings in patients with vitamin D toxicity 5.
• Vitamin D toxicity can also cause confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration 3.