Hi, all.
As far as I can tell, the reason why the FDA has limited the dosage of over-the-counter potassium supplements to less than 100 mg per pill is to prevent damage to the digestive tract when too much potassium is concentrated at one place.
As has been noted, the daily requirement for potassium is much higher than this, and the Institute of Medicine has not assigned an upper limit for potassium supplementation. When potassium is distributed, such as in food or in a solution, this problem of concentrating at one place does not occur.
The main problems with going too high on potassium intake are due to high levels in the blood (hyperkalemia) which can occur in people who do not have normal kidney function, so that they are not able to excrete the excess.
One concern I would have in ME/CFS is that two studies have shown that aldosterone is low in this disorder. Normally, aldosterone acts to increase potassium excretion into the urine when it gets too high in the blood, so low aldosterone may allow the potassium concentration to rise in the blood in ME/CFS. I think it would be wise to check it periodically if potassium is being supplemented at relatively high dosages.
Best regards,
Rich