Fam has covered several topics in her informative post. :)
Just a reminder that people with kidney disease have to be especially careful about their potassium levels. Many kidney conditions and other factors result in an excessive potassium removal through the kidneys. One of these factors is a low level of magnesium - hypomagnesemia.
Magnesium is an important factor for potassium uptake and the maintenance of potassium intracellular levels. This is one of the reasons having a healthy level of magnesium is so important.
Another way the potassium is lost is by being shifted into cells. This shift is stimulated by insulin and glucose, especially after meals, and made possible by beta blockers.
People with reduced kidney function and/or chronic kidney disease who are on diuretics, ACE inhibitors and/or beta blockers should have their K levels carefully monitored. Any potassium-sparing meds MUST be used with extreme caution. Ironically, they can cause hyperkalemia while helping prevent hypokalemia. :(
Hyperkalemia can be caused by ACE inhibitors, beta blockers, alpha blockers, ARBs, potassium-sparing diuretics, NSAIDS and other meds.
Hypokalemia can be caused by beta adrenergic agonists (epinephrine), decongestants, bronchodilators, thiazide diuretics and other meds.
In people with a decreased renal function and the elderly, many medications necessitate a reduction in a dose. Diuretics often require a dose INCREASE so that sufficient levels can be attained at their site of action (in the renal tubules).