​Patient preparation: Ideally patients should be seated or supine (30minutes) prior to sampling. Dietary catecholamine intake has little effect on metanephrine and normetanephrine but may have significant impact on 3-methoxytyramine. Overnight fasting and avoidance of catcholamine rich foods (eg bananas, plums, pineapples, walnuts, tomatoes, avocados, aubergine, alcoholic drinks, vinegar) is advised if measurement of 2-methoxytyramine is likely to be important as a marker of dopamine secretion.