In order to be diagnosed with POTS you must meet specific criteria while standing. It appears from my research POTS doctors do not even agree upon the criteria in which one is to be diagnosed. Below you will find the most strict criteria of POTS I found online.
1) Symptoms have persisted for at least 6 months.
2) Your heart rate increases by at least 30 BPM within 10 minutes upon standing or being upright.
3) This change in heart rate does NOT occur in congruence with a fall in blood pressure >20/10 mmHG
4) No obvious signs of other conditions that would cause these issues such as dehydration or hyperthyroidism.
5) Symptoms are relieved while sitting or lying down.
6) Standing plasma Norepinephrine levels > 600.