How do you tell between 'whit coat hypertension' and real hypertension (high blood pressure)?

One very reliable way to outrule white coat hypertension is a 24 hour ambulatory BP monitor, simply a strap on monitor that takes your blood pressure multiple times during the day and is then seen by your doctor. If you have only white coat htn then it will show a range within normal boundaries. Your doctor would have to arrange this test. A homeBP monitor is relatively easy to get hold of and may give you the same reurance, but is not as reliable.