Lab marker
Zinc (RBC)
Erythrocyte zinc · Red blood cell zinc · Intracellular zinc
Zinc measured inside red cells — pitched as a steadier read on status than plasma, which swings with meals and inflammation.
What it measures
Zinc is essential for immune function, wound healing, taste, and hundreds of enzymes and transcription factors. No single biomarker reliably captures zinc status: plasma/serum zinc is the standard despite falling with infection, stress and recent meals, while red-cell and other cellular measures are used in research to reflect longer-term stores.
Reference context
1 guideline source
Plasma zinc remains the most widely used status indicator despite its limitations; the BOND review concluded that no biomarker is fully satisfactory and recommended interpreting zinc status from intake, plasma zinc and clinical context together.
Population context — consult guideline targets below
Mechanism
Why moving this marker matters
Zinc is a structural and catalytic cofactor across the proteome, including in immune-cell signalling — which is why borderline deficiency is linked to impaired innate and adaptive immune responses. The body has no dedicated zinc store, so continuous intake matters.
Guideline targets
What major guidelines recommend
Typical laboratory interval
RBC ≈180–220 µmol/L; plasma ≈11–18 µmol/L (fasting morning)
No biomarker is a fully satisfactory measure of zinc status.
How to measure
The test, where to get it, when to repeat
Method
Blood draw with the red-cell fraction analysed; plasma zinc is the routine alternative. Collection must avoid zinc-contaminated tubes and skin contact.
Where
Private and specialist labs.
Typical cost
€20–45.
Fasting
Required
When to test
BOND zinc review 2016
No routine population screening; assess in suspected deficiency (poor intake, malabsorption, high demand), interpreting any single biomarker alongside diet and clinical picture.
Where to test
Independent labs offering this test
No direct-to-consumer lab currently in our directory for this marker — your GP can request it on a standard panel.
Context
Reading the numbers
Plasma zinc remains the most widely used status indicator despite its limitations; the BOND review concluded that no biomarker is fully satisfactory and recommended interpreting zinc status from intake, plasma zinc and clinical context together.
Caveats
Chronic high-dose zinc supplementation (>40 mg/day) depresses copper absorption and can cause copper-deficiency anaemia and neuropathy. Inflammation lowers plasma zinc independently of stores. Sample contamination from rubber stoppers and skin is a real pre-analytic risk.
See also
Related markers
Take to your physician
Worth discussing
- Whether your intake and symptoms justify testing at all, given biomarker limitations.
- If supplementing zinc long-term, whether copper status should be checked.
- Whether a low plasma zinc reflects true deficiency or current inflammation.
Sources
Cited literature
Edited by Carl Pöhl, MD · Healicus editorial
Last reviewed May 2026
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