Abby, I want to be clear this is my experience only. I have had the light- headedness and shortness of breath under circumstances that arent to do with my MG per se. I acutally ended up in the ER with it in Nov 08. I thought then it was likely my MG altho I told ER staff in all honesty I had started a diet change tho I didnt see how that would be it. Also it was my first winter on mestinon and had the usual improvement in symptoms which accompanies me needing to reduce the amount I am on as my body DOES act like it is too much. I was down to 30mg from 60mg 3x a day. They called my neuro and she said go back up to 45mg. My family doc who has lost his way took the easy way out and said give me zanax. The doctor told me this and I said I dont need that that has nothing to do with this.

Now what I know about this is that in the diet change I had reduced my dietary sodium. Now that is a big deal for me as I dont eat hardly any processed or fast food which is one of the biggest sources of sodium. Now that I have inceased my salt into my diet per doctors orders I have none of this anymore. My internist told me I have POTS which if salt and water is out of balance, low I get the lightheaded and even breathing and weaker to alot weaker. I am so glad I know what this is now.

Annie59