Taking mega vitamins, or consuming large doses of vitamins, has been considered beneficial to health. However, overdosing on vitamins can cause serious health conditions.
Risks
Health risks from vitamin overdoses vary based on the particular vitamin. While taking too many vitamins at once is rarely cause for alarm, taking too much over an extended period of time can be dangerous. (Ref. 1.)
Vitamin A
Vitamin A is fat soluble and is regarded as one of the most dangerous vitamins, if too much is ingested. Too much can cause hypervitaminosis A, which includes headache and nausea, and sometimes even liver damage. (Ref. 1.)
Vitamin B
A popular vitamin due its linkage with energy, Vitamin B can cause nerve damage over time if excessive doses are taken (100 mg or more a day). (Ref. 1.)
Vitamin C
Considered non-toxic because it is water soluble, Vitamin C, in high doses, has been linked to diarrhea, abdominal pain, and kidney stones. (Ref. 1.)
Prevention/Solution
Excessive intake of Vitamins D and E can also cause adverse conditions. Consult medical professionals when considering mega vitamin supplements. It is very difficult to ingest too