From the Guidelines
Vitamin D toxicity is a rare but potential harm of treatment with oral vitamin D, which may lead to hypercalcemia, hyperphosphatemia, suppressed parathyroid hormone, and hypercalciuria, and is often defined as a 25-(OH)D level above 500 nmol/L [>200 ng/mL] 1. The main signs of vitamin D toxicity include:
- Elevated blood calcium levels (hypercalcemia)
- Hyperphosphatemia
- Suppressed parathyroid hormone
- Hypercalciuria
- Nausea
- Vomiting
- Weakness
- Frequent urination
- Excessive thirst
- Bone pain
- Kidney problems
- Formation of calcium stones In severe cases, confusion, abnormal heart rhythms, and even death can occur. Vitamin D toxicity typically happens when taking extremely high doses of vitamin D supplements (usually above 10,000 IU daily for extended periods) rather than from sun exposure or food sources. Blood tests showing 25-hydroxyvitamin D levels above 150 ng/mL along with high calcium levels confirm toxicity. Treatment involves stopping vitamin D supplementation, limiting dietary calcium, increasing fluid intake, and in severe cases, medications like bisphosphonates or corticosteroids to lower calcium levels. Most people recover fully when the excess vitamin D is eliminated from their system, though kidney damage may be permanent in severe cases. It is essential to note that the safety 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.
From the Research
Signs of Vitamin D Toxicity
- Confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration are common clinical symptoms of vitamin D toxicity (VDT) 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
- Serum 25OHD levels above 150 ng/ml are considered as VDI 3, 2
Laboratory Findings
- Elevated serum 25-hydroxyvitamin D [25(OH)D] concentrations higher than 150 ng/ml (375 nmol/l) are the hallmark of VDT due to vitamin D overdosing 2
- Asymptomatic hypercalcemia caused by the intake of vitamin D even in doses recommended for the general population and considered safe, also known as hypersensitivity to vitamin D 2
Risk Factors
- 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
- Increased public awareness of vitamin D-related health benefits might increase the risk of VDT due to self-administration of vitamin D in doses higher than recommended for age and body weight or even higher than the established upper limit intake values 2
- Inappropriate prescribing, and the use of high-dose over-the-counter preparations or unlicensed preparations 4