What do you advise if i'm told that a symptom (muscle weakness) is a sign of too much potassium, and also that is is a sign of too little potassium. how can this be?

Muscle weakness: High and low levels of potassium (K) can cause muscle weakness. The only way to tell what your K's level is is by a blood test. At your age, with no evidence of any disease, and on no medications. you should not have abnormal K levels. When you have muscle weakness check both your K and magnesium (M), to see if you can implicate an abnormal K as the cause of it. Low M can cause low K levels.