Vitamin D is not actually a vitamin, but a hormone. It is created when your skin is exposed to the sun, and it maintains calcium levels and proper bone formation. MayoClinic.com states that it may help treat osteoporosis, cancer and even high blood pressure. Many people supplement with it for these reasons. Yet, it can be toxic in high doses and cause unwanted effects, such as a rash.
If you supplement with vitamin D, you can take D2 (ergocalciferol) or D3 (cholecalciferol). D2 is synthetic while D3 is naturally occurring. The recommended daily dosage is 400 international units daily. The National Institutes of Health's Office of Dietary Supplements actually lists 600 IUs for adults aged 19 to 50. Milk is supplemented with Vitamin D. You can also get Vitamin D from fish like salmon and tuna. Exposure to sunlight is another source.
Appetite loss, headache, nausea, fatigue and agitation are signs of too much vitamin D, according to Shari Lieberman, Ph.D., and Nancy Bruning, authors of "The Real Vitamin & Mineral Book." Other problems with high doses include calcium deposits in organs, kidney stones, severe headaches and rashes, reports Life Extension.com.
Vitamin D is toxic in high doses. More than 1,000 IUs daily is dangerous. Serious reactions like irregular heartbeats, anorexia, weight loss and frequent urination are other examples of an excess dosage. The longer you take too much vitamin D, the worse the toxicity will be.
Vitamin D and a Rash
It does seem possible to get a rash from too much vitamin D. Some sources list skin rash as a reaction while others do not. Skin rash is not as likely as nausea or other symptoms. Sometimes, fish oil is recommended for individuals to get enough vitamin D. Fish oils are known to cause skin rashes in some people. However, this might be an allergic reaction instead.