How long after receiving an injection of Haldol 5 mg should I see or feel it working?

It's probably going to kick in for less than a week. However, Haldol 5mg injection is on the high side of dosage. I would not recommend that if you are not schizophrenic or suffering dementia. Get off from it if you are using it for other conditions as the side effects are not likely to be reversible. Consult with your psychiatrist or get a 2nd opinion from an experienced MD.