You will likely be told not to eat anything (fast) for 10 hours before the test. You may be allowed to drink water during this time. The accuracy of the test can be affected by certain foods and medicines. Foods that can increase catecholamine levels include: Coffee Tea Bananas Chocolate Cocoa Citrus fruits Vanilla You should not eat these foods for several days before the test. This is especially true if both blood and urine catecholamines are to be measured. You should also avoid stressful situations and vigorous exercise. Both can affect the accuracy of the test results. Medicines and substances that can increase catecholamine measurements include: Acetaminophen Albuterol Aminophylline Amphetamines Buspirone Caffeine Calcium channel blockers Cocaine Cyclobenzaprine Levodopa Methyldopa Nicotinic acid (large doses) Phenoxybenzamine Phenothiazines Pseudoephedrine Reserpine Tricyclic antidepressants Medicines that can decrease catecholamine measurements include: Clonidine Guanethidine MAO inhibitors If you take any of the above medicines, check with your health care provider before the blood test about whether you should stop taking your medicine