It could be. You can OD on vitamins. For example, too much Vitamin A can give you liver damage, among other things.
The trouble with self medicating with vitamins is that you don't know whether your body is actually lacking them or not and too much can be very bad.
Apart from a vitamin B tablet, I do not believe in vitamin pills.
I took vit B when in a mosquito infested area however was told it was an old wives tale. However my partner got Ross River virus and in 10 years I did not.
My chemist husband once said they are all rubbish!