Possible causes of derealization?

[anxietysucks11]

While I had the flu, I constantly thought about when I'd die. Also I had a migraine. Can the flu, migraine, and obsessive thoughts lead to depersonlization??? Help me

[Gambit62]

This is a link to symptoms of B12 deficiency, symptoms of which can include migraine, frequently infections, obsessive thoughts and depersonalisation

pernicious-anaemia-society....

unfortunately there isn't a definitive test for B12 - the serum test requires interpretation in the context of clinical presentation (ie symptoms) but GPs generally aren't aware of that so getting a diagnosis and treatment can be really difficult.