The short answer to this question is: The risks or benefits of long term use of multivitamins are at best questionable.
What this means is that if you have a balanced diet that provides you enough micro nutrients and trace elements, you do not need multivitamins. The proof is in the fact that our grand parents not only survived without them but had long and healthy lives.
If however your diet is defficient you should use multivitamins judiciously: Getting serum levels checked is ideal but if not, I do not see any wisdom in using any more than a bottle a year or six months without any symptoms.
The biggest adverse effect is on your wallet as you would be passing more than half to two thirds of your intake in urine. Oral ingestion is not commonly known to cause hypervitaminosis but the supplements are passed out in urine and stools.
Contrary to popular belief, multivitamins are not a source of energy or strength to the body.
Hope this helps.
Aoa must get yourself checked by a competent physician to reach a proper diagnosis and treatment
Well there are side effects for everything in excess. For how long you have
been taking this ? And who has recommended this you and why ?