Hi Rach, I get these symptoms when my adrenal insufficiency is acting up ...if I have a infection and need more cortisone ( sick day rules). If you say you often have low BP then you should be checked. One type of AI is caused by autoimmune probs and once you have one a/immune disease you are more likely to have others. I know a person with Addisons Disease who has just been dx with MG. A GP can test electrolytes and 8am serum cortisol for you. Do you take steroids already for MG ? In the meantime try to have lots of salty soups and keep up the fluids. ( if you are having the blood test keep to a normal diet though) Try to see the Dr soon. AI can be very serious if not cared for. There is a great UK Assoc. I will send the link to you.