Mirtazapine - Is it normal to feel an increase in anxiety after increasing dose of Remeron?

Hi, avalon!
It's not uncommon to experience some new/increased anxiety when first starting an antidepressant/anxiolytic and after a dosage increase but side effects generally last only a few days to a week or two. If it persists be sure and let your doctor know. Some people need to stay on a lower dose as their metabolism adjusts to the medication.
Most people start feeling some improvement in the first few weeks but it can take up to six weeks or so for the drug to become fully effective.
Best regards,
Wildcat