What are the side effects of taking multivitamins?

I'm curious, could you elaborate on the potential side effects associated with taking multivitamins? Are there any common issues that individuals should be aware of before incorporating them into their daily routine? Additionally, is there a specific dosage or frequency that should be adhered to in order to minimize any adverse reactions? It's important to understand the full scope of considerations when making decisions about supplementation, so I'd appreciate your insights on this matter.