How can i tell if taking too many vitamins is bad for me?

Could be: It depends on what particular vitamins you're talking about. In high doses, some can cause problems -- such as too much b6 can cause neuropathic symptoms, and too much pre-formed vit a can lead to dizziness, nausea, headaches, skin irritation, pain in joints and bones, etc. Here is a helpful resource for safe vitamin amounts: http://tinyurl.Com/7kzonbj.