Zinc

Ranges vary between laboratories (for example 11 to 24 or 10 to 18 umol/L), the value is lower in the afternoon, after meals, in pregnancy and during any inflammation, and the printed range is the one to use.

Zinc is a trace element needed by hundreds of enzymes, for wound healing, taste and smell, the immune system and growth. Most of the body's zinc is inside cells and bone; the blood carries only a small fraction, bound to albumin, and that fraction falls quickly during illness whether or not the body's stores are low.

It is requested when poor wound healing, unusual rashes, hair loss, loss of taste or repeated infections are being looked into, in people with poor absorption, chronic diarrhoea, liver disease, heavy alcohol use or on long-term intravenous feeding, and after weight-loss surgery. It is on many private nutrition panels.

• Zinc supplements, including cold remedies and denture creams containing zinc
• A sample left sitting on the cells before separation, which leaks zinc from the red cells
• Fasting overnight, slightly, compared with after a meal
• Long-term intravenous feeding with too much zinc

• Any inflammation, infection or surgery, which lowers it for days to weeks
• Low albumin, for example in liver disease, kidney protein loss or poor nutrition
• Poor absorption, chronic diarrhoea, Crohn's disease, coeliac disease and weight-loss surgery
• Heavy alcohol use and liver disease
• Pregnancy, the combined contraceptive pill and older age, in the general population
• Diets low in meat and high in unrefined cereals, and some medicines including diuretics
• A recent meal, which lowers it for a few hours

• A cold or any inflammation on the day of the test lowers it, so doctors often read it alongside CRP and albumin
• Afternoon and post-meal samples read lower
• Blood that stood before separation, or was collected in a standard tube rather than a trace-element tube, reads falsely high
• Low albumin lowers the total without lowering what is available

A fasting morning sample in a trace-element tube, separated promptly, ideally not during an infection, with CRP and albumin measured at the same time.

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