Often in CHF you may see spironolactone used in combination with loops and other diuretics to try to help treat edema. There are certainly other indications for spironolactone, but I’ll leave that for another day. My patient was having difficulty with edema and the increasing the loop diuretic was not getting much added benefit from the increase. Spironolactone was added to try to augment the fluid loss and improve CHF symptoms. Spironolactone is a potassium sparing diuretic (it can raise potassium levels in the body which is opposite from loop and thiazide diuretics which deplete potassium). This patient already had a potassium level around 4.8 prior to the addition of the spironolactone with the upper end of normal of about 5.0. A couple weeks after initiation of the spironolactone, follow up electrolytes and kidney function labs were drawn and the potassium level was around 5.9 necessitating the discontinuation of spironolactone. Bottom line, spironolactone can increase potassium levels.