Plasma normetanephrine

Cut-offs vary with the laboratory, rise with age on some methods, and are higher for a seated than a lying sample, so the printed cut-off is the one to use.

Normetanephrine is the breakdown product of noradrenaline, the nerve messenger that keeps blood pressure up and tightens blood vessels. It is measured with metanephrine as the main blood test for phaeochromocytoma and the related nerve-tissue tumours called paragangliomas, which more often make noradrenaline than adrenaline.

It is requested with metanephrine when episodes of headache, sweating and palpitations with high blood pressure are being looked into, when an adrenal lump is found on a scan, when blood pressure is difficult to control, and in families with inherited tumour conditions.

• Phaeochromocytoma and paraganglioma, which more often make noradrenaline
• Stress, pain, anxiety and a difficult blood draw
• Sitting up rather than lying down for the sample
• Some medicines, including tricyclic antidepressants, venlafaxine, decongestants and levodopa
• Caffeine, nicotine and recent heavy exercise
• Sleep apnoea, heart failure, kidney disease and acute illness
• Older age, in the general population

• A value below the cut-off is the expected finding
• Some blood pressure tablets can lower it slightly
• After removal of the tumour the expected level is below the cut-off

• A stressful blood draw or sitting up for the sample can push it above the cut-off
• Tricyclic antidepressants and venlafaxine are common reasons for a raised value
• Sleep apnoea, heart failure and kidney disease raise it
• Older people run higher

As for metanephrine: taken after lying quietly for 20 to 30 minutes, fasting, without caffeine, nicotine or strenuous exercise beforehand, with some medicines paused first under medical supervision. It is sent to a specialist laboratory.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.