Which vitamins should i be careful with if i try orthomolecular medicine?

Depends...: The vitamins to be most cautious of are the fat soluble ones. The most important part of this approach is to work with a doctor who has knowledge and experience in this area. Ask what training they've had and how long they've been doing it. I prefer to do testing before prescribing anything. Having said that, there have been no deaths in the last 10 years from vitamins.

Orthomolecular Meds: Working with a physician skilled in Functional Medicine would be helpful, if interested in orthomolecular approaches. Functional medicine physicians care for people through addressing root causes. Treatments are often diet and nutritional supplements, as indicated. The Institute for Functional Medicine (https://www.ifm.org/) has a search engine for qualified professionals in your area. Good luck!