Zinc (fingerstick)

Zinc is a trace element: a mineral the body needs only a little of. It is part of many enzymes and is needed for building proteins, growth, wound healing and the immune system. Almost all zinc is in the cells; only a very small part is in the blood, where it is mostly bound to the protein albumin. This analysis measures the zinc in the blood.

• A severe zinc deficiency, for example with bowel diseases causing poor absorption (Crohn's disease, celiac disease, after bowel surgery) or long-term artificial feeding
• Too much zinc from long-term high-dose supplements, which can cause a copper deficiency

• Preferably do not eat for 8 hours before the sample is taken and drink only water. Zinc in your blood drops after a meal.
• Preferably have your blood taken in the morning, because zinc in your blood drops during the day.

With a low zinc, the GP checks whether there was inflammation or infection and repeats the measurement in the morning if needed, together with CRP and albumin. With a clear and persistent deficiency, the GP looks for a cause, such as a bowel disease. With a raised zinc, supplement use is checked and copper is sometimes measured.

Zinc in the blood is an insensitive measure of the body's zinc stores: the body keeps the blood value stable for a long time, and inflammation, time of day and meals often change the value more than a mild deficiency does. According to the Health Council of the Netherlands, the signs of a zinc deficiency are not specific and it is difficult to link a deficiency to symptoms. In people without symptoms, a single value therefore says little.

• Inflammation or infection lowers the value temporarily, even without a deficiency.
• The time of the blood draw and a meal beforehand affect the result; a morning blood draw on an empty stomach gives the most comparable value.
• Hemolysis and contamination with zinc from the skin or materials, especially with a finger prick, can falsely raise the value.
• Zinc supplements raise the value; reference values differ per laboratory.

How often a zinc deficiency occurs in the Netherlands is not well known; according to the Netherlands Nutrition Centre (Voedingscentrum), signs of a deficiency are, as far as is known, rare. The Health Council of the Netherlands considers the zinc intake of the average Dutch population adequate. In model calculations in which all meat and dairy were replaced by plant-based products, zinc intake did fall below the recommendation.

Useful when a severe deficiency is suspected, for example with bowel diseases causing poor absorption, after bowel surgery or with malnutrition, and with long-term use of high doses of zinc supplements. With a vegetarian or vegan diet, zinc intake can be lower, but the blood value does not reliably show a mild deficiency. In healthy people without symptoms, a deficiency is rare and the result says little.

• A slightly low value due to inflammation or the time of the blood draw is easily read as a deficiency; this can lead to unnecessary use of zinc supplements, which cause a copper deficiency at long-term high doses.

• Voedingscentrum: Zink
• Gezondheidsraad: Voedingsnormen voor vitamines en mineralen voor volwassenen (2018), met achtergronddocument
• Gezondheidsraad: Gezonde eiwittransitie (2023)
• Voedingscentrum: Koper