There are some fat soluble vitamins such as vitamin A, D, E and K. If you take too much of any of these vitamins, there are some side effects that you would face. The fat soluble vitamins would not get out of the body through urine. Water soluble vitamins such as Vitamin B and C would go to the urine in case you take too much of it but too much of those vitamins are also not free of risk. For example:
Vitamin B3 (niacin) in doses greater than 300 mg daily may cause headache, nausea, skin tingling, and flushing. Vitamin B6 in doses greater than 250 mg daily may cause reversible nerve damage.
Too much methylated form of vitamin B ( in patients who have MTHFR mutation) also has some side effects.
Unless nutritional testing indicates vitamin C or E deficiency, we recommend that patients obtain adequate doses from dietary sources, including fruits, nuts, and vegetables.
Interactions of different phytochemicals with vitamin C and E and other antioxidants likely provide additional beneficial effects.
A multivitamin or antioxidant formula should provide mixed tocopherols to contain all eight natural isoforms (instead of synthetic alpha-tocopherol) with a daily dose of 200to 400 IU of vitamin E and 500 to1000 mg of vitamin C.