Please tell me what can hallucinations be a sign of?

Hallucinations. Hallucinations can be a sign of multiple possible problems including drug intoxication, drug or alcohol withdrawal, some medications, psychotic depression, bipolar disorder, brief psychotic reactions, schizophrenia, schizoaffective disorder, etc. Hallucinations can also come from delirium secondary to other medical illnesses. If you think you're hallucinating, please see a physician asap.