Zinc
What it measures, and what changes the number.
This test measures the amount of zinc in serum. Zinc is a trace mineral involved in many enzymes, immune function, wound healing, taste and growth. Most zinc in the body sits inside cells, so the blood level reflects only a small part of the total.
It is often read with albumin, since much of the zinc in blood is carried by albumin, and with other minerals such as magnesium, copper or iron when nutrition is being assessed.
Zinc levels fall after meals and vary with time of day, so a morning fasting sample is often requested. Inflammation and infection lower blood zinc. Handling matters a great deal: special trace-element tubes are used to avoid contamination, hemolysis releases zinc from red cells, and the serum should be separated promptly. Spanish labs may print it as Zinc en suero.