Maybe y'all know this but apparently dehydration can cause POTS symptoms as can low adrenal function. Here's what I find about adrenal function (see #4 regarding POTS symptoms): To explore adrenal issues, read up here:faq/ 1) What are the symptoms of adrenal problems? Fatigue, anxiety, light-headedness, shakiness, dizziness, nausea, and difficulty dealing with stressful situations. Dr. Rind says “Most people have a mixture of poor thyroid and poor adrenal function rather than purely one or the other, and therefore a mixture of symptoms”. He also says that poor thyroid and/or adrenal function is the most common cause of low metabolic energy. Metabolism is defined as the chemical changes in living cells by which energy is provided for vital processes (Websters). Please refer to this chart of symptoms http://www.drrind.com/therapies/metabolic-symptoms-matrix 2) How can I tell if my problems are adrenal, or thyroid? The body’s temperature drops as the metabolism drops. Low temperatures are caused by low thyroid. If the adrenal hormone cortisol is low, the average daily temperature will fluctuate when comparing one day’s average to the next. (See Discovery Step Two, number Four, here.) We are not talking about temperature changes during one day – it is normal to wake up with lower temperatures and hitting a peak in the later afternoon. Take your temperature 3 hours after waking, again 3 hours later, and again in another 3 hours. You average those 3 readings to get one single number for that day. Please read Janie’s page  and follow her link to Dr. Rind. Look at his examples and download his blank chart. Begin filling in your temperatures. If you post a question about your dosing, someone is going to ask about your temps. 3) What is Adrenal Insufficiency? In 1855, Thomas Addison first described adrenal insufficiency, which was subsequently named after him. Originally, tuberculosis was the most common reason for the adrenal gland failure. Currently, Addison disease most commonly results from autoimmune destruction of the adrenal gland. The adrenal hormones Cortisol and Aldosterone are vital for life, so Addison’s disease can be fatal. If you search for information on Addison’s disease, you fill find quotes such as this one: “Adrenal insufficiency occurs when at least 90 percent of the adrenal cortex has been destroyed.” http://endocrine.niddk.nih.gov/pubs/addison/addison.aspx 4) Is Adrenal Fatigue the same thing as Adrenal Insufficiency? No. The person with Adrenal Fatigue may have less severe symptoms, and there are lots of shades of gray. Here is an example from a medical site: “A significant number of patients with partial loss of adrenal function (limited adrenocortical reserve) appear well but experience adrenal crisis when under physiologic stress (eg, surgery, infection, burns, critical illness)”  A person with a more serious case of adrenal fatigue may have chronic symptoms of fatigue. They may have symptoms associated with low blood sugar (one of cortisol’s jobs is to help regulate glucose). They may feel light headed upon standing, as another function of cortisol is to maintain blood pressure. Dr. Ron Kennedy says “Addison’s disease is so rare, and adrenal fatigue so common, that I prefer to spend most of our space here on the latter. This syndrome is marked by loss of energy with the experience of fatigue and oversleeping”. http://www.medical-library.net/content/view/75/41/ Dr. Tintera was making comments like this way back in 1955 “a former hypothesis – that the adrenal cortex functioned according to the classic “all or none” law – is repudiated as being contrary to both clinical and experimental evidence. Hypoadrenocorticism may be congenital or acquired, complete or partial. The two former subdivisions frequently fail of recognition.” http://www.fred.net/slowup/tint01.html Many members discovered their adrenal fatigue when they started thyroid medication – because the increased metabolism strained the adrenals. -learned Doctor Broda Barnes describes this in his lectures “And the thing that we have to think of very often, is a partial adrenal deficiency too. If the blood pressure of a patient is 100 systolic or below, I hesitate, in fact I won’t start them on thyroid, without giving them 5mg of prednisone at the same time. Because, if you raise the metabolism a little as we’re doing with the thyroid, you also have to have a little more secretion from the adrenal. The normal gland, can furnish it and do all right. But if the blood pressure is too low in the beginning, the chances are that this patient is going to get worse, about four days after you start them on thyroid, they will become worse than they were.” (5 mg of Prednisone is = to 20 mg of hydrocortisone) 5) How do I test the condition of my adrenals? Please read what Janie says here  If your doctor insists on blood tests for cortisol, they are only going to show the combo of bound and unbound. Doesn’t work. http://www.stopthethyroidmadness.com/recommended-labwork/ etc. (there is lots more) And here is what I found on dehydration:http://www.nymc.edu/fhp/centers/syncope/orthostatic_intolerance.htm A simple and common example of this is the finding of postural hypotension and postural tachycardia when dehydrated. Wiki:http://en.wikipedia.org/wiki/Orthostatic_intolerance Physicians who specialize in treating OI agree that the single most important treatment is drinking more than two liters (eight cups) of fluids each day. A steady, large supply of water or other fluids reduces most, and for some patients all, of the major symptoms of this condition. Typically, patients fare best when they drink a glass of water no less frequently than every two hours during the day, instead of drinking a large quantity of water at a single point in the day. ------- The latter also lists meds for OI you can look up if interested,.