Type IV RTA is characterized by hyperkalemia, normal AG metabolic acidosis, and disturbances in the renin-aldosterone axis leading to impaired release or action of aldosterone. Most patients have concomitant chronic kidney disease, most commonly diabetic nephropathy and interstitial nephritis. Other causes or contributing factors include HIV, sickle cell disease, urinary tract obstruction, lupus nephritis, amyloidosis, myeloma, adrenal insufficiency, kidney transplant rejection, and a variety of medications, such as cyclosporine, ACE inhibitors, angiotensin receptor blockers (ARBs), NSAIDs, trimethoprim, heparin, and potassium-sparing diuretics. In these patients, it is important to differentiate type IV RTA from uremic metabolic acidosis. The urine pH in most patients with type IV RTA is acidic, usually ≤ 6.0, but may be elevated. The acidosis is usually mild, and bicarbonate therapy may not be needed. In the majority of cases, hyperkalemia causes the metabolic acidosis through its effects on renal ammonia metabolism. Accordingly, correcting the hyperkalemia with dietary modification typically corrects the metabolic acidosis. Loop or thiazide diuretics may be necessary in some patients. Sodium bicarbonate may be needed if persistent metabolic acidosis is present despite correction of the hyperkalemia. Exogenous mineralocorticoid therapy should be avoided in patients with chronic kidney disease, since mineralocorticoids can contribute to worsening of renal function. We generally do not recommend discontinuing ACE inhibitors or ARBs in patients with type IV RTA, because of the important effects of these medications to decrease cardiovascular events and to slow the progression of chronic kidney disease.