Vitamin D is essential, but more isn’t necessarily better. Excessive vitamin D—usually from high-dose supplements rather than food or sunlight—can raise calcium levels in the blood and cause toxicity. Office of Dietary Supplements+1
4 warning signs you may be taking too much vitamin D
1. Nausea, vomiting, or loss of appetite
Too much vitamin D can cause high blood calcium (hypercalcemia). Early symptoms can include nausea, vomiting, poor appetite, and abdominal discomfort. Office of Dietary Supplements
2. Excessive thirst and frequent urination
High calcium levels can make you unusually thirsty and urinate more frequently. Dehydration can develop as a result. Office of Dietary Supplements
3. Muscle weakness, fatigue, or confusion
Vitamin D toxicity can produce muscle weakness, tiredness, confusion, or other neurological symptoms, particularly when hypercalcemia becomes significant. Office of Dietary Supplements+1
4. Kidney stones or kidney problems
Excess vitamin D increases calcium absorption and can contribute to high urinary calcium and kidney stones. Severe toxicity can damage kidney function and, in extreme cases, cause kidney failure or abnormal heart rhythms. Office of Dietary Supplements
How much is too much?
For most adults, the U.S. National Institutes of Health lists 4,000 IU (100 mcg) per day as the tolerable upper intake level from all sources. This is a safety limit for routine intake, not a target dose. A doctor may temporarily prescribe higher doses to treat a documented deficiency. Office of Dietary Supplements
Vitamin D toxicity generally occurs from excessive supplementation, not ordinary sun exposure. Office of Dietary Supplements
If you’re taking a high-dose vitamin D supplement and have several of these symptoms, it’s sensible to contact a healthcare professional rather than simply continuing the supplement. A blood test for 25-hydroxyvitamin D and calcium can help determine whether excessive vitamin D is involved.
