not sure

Im not aure if Im in right place.But Im a 51 year old female,smoke,I am on meds for blood preasure ,but I have at times not always that Ill be setting or standing and my whole body will be getting a numb tingely fealing to a point where Im fealing like passing out.And it feals really hot,then Im really cold ..have collapesed from this,but docors found nothing.

[Cleveland Clinic, MD]

I am happy to address the questions that you pose, although it is important that you recognize that my impression is based entirely on the information you have provided in your posting and is by no means a substitute for an office visit with a neurologist.  Diagnosis is contingent on detailed history and physical exam and as such, the following information should be considered solely for educational purposes.

Yours symptoms might reflect a possible problem with the autonomic nervous system that regulates blood pressure, heart rate, temperature (through sweating control) and many other things in the body like bowel and bladder function. some people have a defect in this system or part of it that results in symptoms like fluctuation in the blood pressure and heart rate; which causes the symptoms of lightheadedness and feeling that you are about to pass out, and this sometimes results in actually passing out because of a significant drop on the blood pressure. other symptoms include change in sweating or intolerance to temperature changes and that again is caused by defect in the sweating mechanism that is regulated by the autonomic system.

This sound like the most likely possibility in your case based on the symptoms you described. However is still crucial to get a detailed history and perform a thorough examination that includes checking blood pressure and heart rate in various body positions to detect significant changes. Then there are some specific tests that can assess the autonomic nervous system, these include some cardiovascular tests, a test called tilt table testing, and a sweat test. All these are designed to detect problems with the autonomic nervous system. Depending on the results of the workup some measures can be taken to manage this condition, like improve fluid intake, make some diet adjustments and some other more specific measures.

I advice you to see a specialist like a neurologist who manages autonomic dysfunction. That would be my first choice, there are a couple of neurologists with special interest in autonomic dysfunction at the Cleveland Clinic (Dr. Shields, Dr. Chemali). some places have a dedicated "syncope clinic" as well, which is usually staffed by cardiologists.  

thanks for using the forum, I hope you find more answers soon.