From the Guidelines
Elevated Vitamin D levels above 100 ng/mL can be potentially toxic and require immediate attention, including reducing or stopping vitamin D supplements and consulting a healthcare provider. High vitamin D levels, known as hypervitaminosis D, can occur from excessive supplementation rather than from sun exposure or food sources 1. Normal vitamin D levels range from 20-50 ng/mL (50-125 nmol/L), with levels above 100 ng/mL (250 nmol/L) considered potentially toxic 1.
Symptoms and Treatment
Symptoms of vitamin D toxicity include:
- Nausea
- Vomiting
- Weakness
- Frequent urination
- Kidney problems
- Calcium buildup in the blood which can lead to confusion, heart rhythm abnormalities, and bone pain 1. Treatment typically involves stopping vitamin D supplements, limiting calcium intake, increasing fluid intake, and possibly medications like bisphosphonates or corticosteroids in severe cases.
Prevention and Safety
To prevent high levels, don't exceed the recommended daily allowance (600-800 IU for most adults) unless directed by your doctor, and get regular blood tests if you take supplements long-term 1. A daily intake of 25(OH)D3 up to 4,000 IU is deemed to be the upper limit of safety, as the risk of harm appears to increase above this level 1. However, individual variations in vitamin D-hormone production and metabolism may depend significantly on genotype, phenotype, and environmental conditions, making it difficult to categorize any one of the numerous effects of vitamin D as necessarily beneficial or toxic 1.
Key Considerations
It is essential to note that levels above 100 ng/mL should be considered as a safety limit but not as an upper limit to target in clinical practice 1. The position of all individual participants regarding the range for serum 25(OH)D levels is indicated in Appendix 1, and a summary is presented in Table 2 1. Additionally, excess vitamin D-hormone supplements also displace the active form from binding sites, making it more available even when not appropriate, and may have physiological effects similar to those of glucocorticoids, estrogen, or even those of anabolic steroids 1.
From the Research
Implications of Elevated Vitamin D Levels
Elevated levels of 25-hydroxyvitamin D can have several implications, including:
- Hypercalcemia, which can lead to acute kidney injury and other complications 2, 3, 4, 5
- Hypercalciuria and hyperphosphatemia, which can cause tissue and organ damage 4
- Vitamin D intoxication, which can occur even without developing hypervitaminosis D 4
- Hypersensitivity to vitamin D, which can reflect dysregulated vitamin D metabolism 5
Clinical Symptoms of Vitamin D Toxicity
The clinical symptoms of vitamin D toxicity include:
- Confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration 5
- Nausea, vomiting, and muscle weakness 2
- Fatigue, gastrointestinal complaints 3
Risk Factors for Vitamin D Toxicity
The risk factors for vitamin D toxicity include:
- Excessive long-term intake of vitamin D 5
- Malfunctions of the vitamin D metabolic pathway 5
- Coincident disease that produces the active vitamin D metabolite locally 5
- Inadvertent or improper intake of extremely high doses of pharmacological preparations of vitamin D 5
- Manufacturing errors of vitamin D-containing supplements 3
Diagnosis and Treatment of Vitamin D Toxicity
Diagnosis of vitamin D toxicity is typically made by measuring serum 25-hydroxyvitamin D concentrations, which should be higher than 150 ng/ml (375 nmol/l) 5. Treatment of vitamin D toxicity usually involves stopping vitamin D supplementation, intravenous hydration, and other medications to manage hypercalcemia and acute kidney injury 2, 3.