Patient should be ambulatory / upright 2 hours prior to test. Medications for Potassium wasting diuretics, Spironolactone, Eplerenone, Amiloride and Triamterene should be discontinued at least for 4 weeks; Adrenergic blockers, Clonidine, Methyldopa, NSAIDs, Angiotensin-converting enzyme inhibitors, Angiotensin receptor blockers, Renin inhibitors and Dihydropyridine calcium channel antagonists should be discontinued for 2 weeks. If necessary to maintain hypertension control, patients should be treated with other antihypertensive medications like Verapamil slow-release, Hydralazine, Prazosin.