Autonomic neuropathy can be a debilitating condition and greatly affect your quality of life.

You've obviously had some testing (tilt table) for the POTS, but you don't mention what (if any) treatments you are receiving. For mild cases there are life style changes, increased sodium intake, proper attention to hydration, etc. But yours sounds more severe and may require other intervention.

There are a few medication to help increase BP. Midodrine and Florinef are first line treatments for moderate to severe orthostatic hypotension. Midodrine is a vaso-constrictor which helps to keep blood from pooling in your feet upon standing. Florinef is a mineral steroid that works by helping the body to retain fluids, which in turn increases BP.

Usually doctors start with one of these and it can take a while to modify dose or add the other medication if needed. You need to pay attention to your body when upright for sign that you will pass out...increased heart rate, sweating, weakness in your legs, and of course, the most common--lightheadedness and dizziness. As soon as you feel any of these coming on, you need to sit down immediately. Symptoms can easily be reversed by getting your feet elevated. If you are in a location where sitting is not an option, then walk...the contraction of muscles will help to increase BP a little...hopefully long enough to get to a place to sit. Also keep water with you as you can increase BP fairly rapidly by drinking water.

Of course the best treatment is to address the underlining cause, but you may not know what that is. So you do the best you can what options available. You really need the help of a good autonomic specialist or cardiologist to manage your BP meds.

The heart rate sometimes settles down once you get the BP under better control...as the heart rate increases are usually compensatory to the low BP (the heart knows the BP is low so pumps faster to compensate).

Hope this is helpful. Have you had other autonomic testing like QSART, 24 hour BP, holter monitor, etc?