While vitamin D is essential for hair growth, too much of it can potentially lead to hair loss. A balanced level of vitamin D helps in the creation of new hair follicles and stimulates the cells that add strength to the hair.
However, an overdose of vitamin D, called hypervitaminosis D, can lead to several health issues. As per the Mayo Clinic, this can cause symptoms such as nausea, vomiting, weakness, and frequent urination. Problems with heart rhythm might occur and kidney stones or damage could also result.
It's crucial to note that hair loss is generally not the first symptom of an overdose of vitamin D, and other symptoms usually appear first. Moreover, such an overdose is rare and usually occurs from taking high-dose supplements for a long period.