?A zinc blood test can help identify an abnormally low or high concentration of zinc in the blood, but the result is more sensitive to timing, food intake and illness than many people realise.
That matters when investigating possible low zinc.
Serum or plasma zinc is widely used in clinical practice to assess zinc status, yet it does not perfectly reflect the body's total zinc stores. Zinc concentrations can change with the time of day, recent meals, infection, inflammation and other physiological factors.
A single result therefore needs context.
A low measurement may support zinc deficiency when it fits with dietary risk, malabsorption, symptoms or another relevant medical condition. A normal result does not prove that every tissue has an ideal zinc concentration, but it should not simply be dismissed either.
London Blood Tests offers a private Zinc Blood Test for people who require an individual zinc measurement, with clinic and home blood collection options.
What Is a Zinc Blood Test?
Zinc is an essential trace mineral required for numerous biological processes.
It contributes to normal immune function, DNA and protein synthesis, cell division, wound healing, growth and the senses of taste and smell.
Most zinc in the body is stored in skeletal muscle and bone rather than circulating freely in the bloodstream.
A zinc blood test measures the concentration present in a blood sample.
You may also see people searching for:
zinc test
zinc blood work
zinc deficiency test
Zn test
These terms may describe different laboratory methods depending on the provider, so the sample type and laboratory reference information should always be checked.
What Does a Zinc Blood Test Actually Tell You?
Serum or plasma zinc is commonly used as a practical clinical measure of zinc status.
A low result can support suspected deficiency, particularly when there are relevant symptoms or risk factors.
However, zinc testing has recognised limitations.
The concentration can be influenced by:
recent food intake,
time of day,
infection or inflammation,
age and sex,
changes in hormones,
illness and muscle breakdown,
and laboratory collection conditions.
This means zinc is not a biomarker that should always be interpreted from one number in isolation.
The most useful assessment considers the laboratory result alongside nutritional intake, digestive health, medicines, supplementation and the reason the test was requested.
Can a Blood Test Detect Zinc Deficiency?
A low serum or plasma zinc concentration can provide evidence of inadequate zinc status.
But no single blood measurement perfectly describes all zinc within the body.
This distinction is important because it is easy to move from the correct statement:
"serum zinc has limitations"
to the much stronger and less defensible claim:
"serum zinc cannot detect deficiency."
That is not accurate.
Serum and plasma zinc remain commonly used in clinical practice.
The limitation is that interpretation needs context.
If the result is low and the person also has a restricted diet, gastrointestinal disease, poor absorption or characteristic clinical features, the evidence for genuine deficiency becomes stronger.
If the result is unexpected and the sample was taken during illness or without appropriate preparation, repeating the measurement may sometimes be more informative.
Can Zinc Be Low During Infection or Inflammation?
Yes.
This is one of the most important points when interpreting a zinc test.
Serum zinc can fall during the body's acute inflammatory response.
That means someone who has an infection or significant inflammatory illness may temporarily have a lower circulating zinc concentration even if poor dietary zinc intake is not the main problem.
This phenomenon makes timing important.
A low result obtained during acute illness should therefore be interpreted differently from a persistent low result in someone who is otherwise well.
This is also why London Blood Tests generally recommends waiting until a short-term illness or infection has resolved before routine nutritional testing where clinically appropriate.
If inflammation itself is being investigated, our guide to CRP and ESR blood tests explains how inflammatory markers answer a different clinical question from nutritional zinc testing.
Does the Time of Day Affect Zinc Results?
Yes.
Circulating zinc shows diurnal variation, meaning concentrations can change over the course of the day.
Food also causes fluctuations.
Some UK laboratory guidance therefore recommends morning collection using a fasting sample when accurate zinc assessment is required.
This becomes particularly relevant when comparing two results.
A zinc sample taken fasting at 9am should not necessarily be compared casually with another sample taken shortly after lunch at 4pm and interpreted as though the difference must represent a genuine change in zinc status.
Consistency improves interpretation.
Do You Need to Fast for a Zinc Blood Test?
Laboratory preparation requirements can vary, but fasting may be recommended for zinc testing because meals can cause significant changes in circulating zinc concentrations.
Where fasting is requested, an overnight fast is usually the most practical approach.
Water is normally permitted.
Follow the preparation instructions provided for the specific laboratory performing your test rather than assuming that all zinc assays use identical protocols.
London Blood Tests advises patients to follow the preparation instructions associated with their particular test and generally recommends morning collection where possible.
What Causes Low Zinc?
A low zinc concentration can have several possible explanations.
Inadequate Dietary Intake
Zinc is found in foods including meat, shellfish, dairy products, eggs, beans, nuts and whole grains.
People eating very restricted diets may have lower zinc intake.
Plant-based diets can still contain zinc, but the mineral can be less bioavailable because compounds called phytates in grains, legumes and seeds can bind zinc and reduce its absorption.
This does not mean vegetarian or vegan diets automatically cause zinc deficiency.
It means intake and bioavailability may deserve consideration when other risk factors are present.
Gastrointestinal Disease and Malabsorption
Conditions affecting the gastrointestinal tract can reduce zinc absorption or increase losses.
These may include inflammatory bowel disease, coeliac disease and some situations following gastrointestinal or bariatric surgery.
Chronic diarrhoea can also contribute to zinc loss.
Someone with persistently low zinc and ongoing gastrointestinal symptoms may therefore need assessment of the underlying digestive problem rather than simply taking progressively larger zinc supplements.
Poor Overall Nutrition
Malnutrition, very low caloric intake and eating disorders can affect zinc alongside other vitamins and minerals.
In these circumstances, zinc should rarely be considered in isolation.
Alcohol-Related Problems
Chronic excessive alcohol intake can contribute to poor zinc status through reduced dietary intake, impaired absorption and increased urinary losses.
Increased Losses
Major burns, chronic wounds and some medical conditions can increase zinc requirements or losses.
The relevant clinical context matters when interpreting a low result.
What Are the Symptoms of Zinc Deficiency?
Zinc deficiency symptoms vary according to the degree and duration of deficiency.
Possible features can include:
impaired wound healing,
changes in taste or smell,
poor appetite,
hair loss,
skin changes,
frequent or prolonged infections,
and impaired growth in children.
More severe deficiency can affect several organ systems.
But none of these symptoms proves zinc deficiency.
Hair loss, for example, can also be associated with iron deficiency, thyroid disease, hormonal changes, stress, autoimmune conditions and many other causes.
Similarly, frequent infections do not automatically mean that zinc is low.
A zinc deficiency test can provide objective laboratory information where deficiency is genuinely suspected, but it should be used as part of a wider assessment.
Can Low Zinc Cause Hair Loss?
Zinc deficiency can contribute to hair loss in some people.
However, it is not one of those relationships where:
hair loss = zinc deficiency.
Hair shedding and thinning have numerous possible causes.
Iron status, thyroid function, hormonal changes, illness, nutritional restriction and dermatological conditions may all need consideration.
For people with broader nutritional concerns rather than a specific reason to test zinc alone, the London Blood Tests Nutritional Health Profile includes zinc together with vitamin D, B12, folate, iron studies, magnesium and other health markers.
That may provide more useful context when several nutritional deficiencies are being considered.
Can Zinc Deficiency Affect Wound Healing?
Yes.
Zinc plays an important role in cell division, protein synthesis and tissue repair.
Clinically significant deficiency can therefore impair wound healing.
However, slow wound healing also has other important causes, including diabetes, poor circulation, infection and nutritional deficiencies unrelated to zinc.
A wound that is persistent, infected or failing to heal requires appropriate clinical assessment.
A zinc result can add information.
It should not substitute for assessment of the wound itself.
Zinc and the Immune System
Zinc contributes to the normal development and function of several components of the immune system.
Deficiency can impair immune responses.
This biological relationship sometimes leads to an exaggerated marketing claim that taking additional zinc will universally "boost immunity".
That is too simplistic.
Correcting genuine deficiency is different from taking increasing doses of zinc when zinc status is already adequate.
More is not automatically better.
This distinction becomes particularly important because excessive zinc intake can create its own nutritional problems.
Can Too Much Zinc Be Harmful?
Yes.
Zinc is essential, but excessive long-term intake can be harmful.
One of the most important consequences is interference with copper absorption.
High supplemental zinc intake over time can contribute to copper deficiency.
Copper deficiency can then lead to haematological and neurological problems in severe cases.
Excess zinc may also cause nausea, vomiting, abdominal discomfort, reduced appetite and other gastrointestinal symptoms.
The NIH Office of Dietary Supplements currently sets the tolerable upper intake level for zinc at 40 mg per day for adults from all sources, although medically prescribed treatment may use different doses under supervision.
This is one reason supplementation should not simply aim to push zinc as high as possible.
The objective is adequate zinc status—not excess.
Zinc and Copper: Why Balance Matters
Zinc and copper interact during intestinal absorption.
High zinc exposure can induce proteins in intestinal cells that bind copper and reduce the amount absorbed into the circulation.
This is particularly relevant to people taking high-dose zinc supplements for prolonged periods.
If someone is supplementing heavily with zinc and develops unexplained anaemia, neurological symptoms or other concerning features, copper status may need consideration.
A broader Mineral Screen (Whole Blood) available through London Blood Tests includes red-cell zinc together with copper, selenium, magnesium, calcium, potassium, chromium and manganese.
A broader mineral panel is not necessary for everyone taking a multivitamin.
It becomes more useful when there is a genuine question about multiple mineral abnormalities or long-term supplementation.
What Does a High Zinc Blood Test Mean?
A high blood zinc result is less commonly encountered than low zinc.
Possible explanations include recent supplementation, high-dose zinc use or sample contamination.
Collection technique matters particularly with trace elements.
NHS laboratory guidance notes that zinc testing can be affected by inappropriate tubes, haemolysis and contamination from some collection materials.
An unexpectedly high result therefore sometimes warrants confirmation before conclusions are drawn.
Persistently high zinc in someone taking supplements also raises the question of excessive intake and potential copper imbalance.
Do not assume that a high zinc result is beneficial.
Why Sample Collection Matters for Zinc Testing
Trace-element testing has more demanding pre-analytical requirements than many routine blood tests.
The collection tube itself can matter.
Some materials can contaminate samples with trace amounts of zinc, producing inaccurate results.
Haemolysis can also interfere with interpretation because blood cells contain zinc.
UK laboratories may therefore specify trace-element collection tubes rather than ordinary serum separator tubes.
This is one reason zinc testing should be performed using the collection instructions supplied by the analysing laboratory.
A correctly ordered test can still produce misleading information if the specimen is collected or handled incorrectly.
Serum Zinc vs Red Cell Zinc
London Blood Tests offers both a standard Zinc Blood Test and a Red Cell Zinc Test.
They assess zinc in different blood compartments.
Serum or plasma testing measures circulating zinc and is widely used clinically.
Red-cell testing measures zinc associated with erythrocytes.
Because much of the body's zinc is intracellular, red-cell zinc is sometimes used as an alternative or additional assessment.
However, this distinction should not be simplified into:
"red-cell zinc is always more accurate."
Serum/plasma zinc has recognised limitations, particularly its sensitivity to meals, inflammation and timing.
But alternative intracellular measures also have methodological and interpretative limitations, and there is no single laboratory marker that perfectly reflects total-body zinc status in every person.
The appropriate test depends on the clinical question and the laboratory methodology being used.
Is Red Cell Zinc Better for Long-Term Zinc Status?
It may provide different information, but "better" is too broad a claim.
Red blood cells circulate for several months, which creates a theoretical basis for red-cell mineral testing being less sensitive to very short-term changes than serum measurements.
However, clinical interpretation is less standardised than routine serum or plasma zinc testing.
This is why I would not automatically escalate from a normal serum result to a red-cell test simply because symptoms remain unexplained.
Persistent symptoms may be caused by something other than zinc.
The next investigation should follow the clinical problem rather than repeatedly testing the same nutrient using different compartments until an abnormal value appears.
Is Zinc Included in Routine Blood Tests?
Usually not.
A Full Blood Count does not measure zinc.
A routine kidney profile does not usually measure zinc.
A standard liver function test does not measure zinc either.
Zinc generally needs to be requested specifically or included within a nutritional or mineral profile.
London Blood Tests' Nutritional Health Profile, for example, includes zinc alongside magnesium, vitamin D, vitamin B12, folate, iron studies and a number of other markers.
For a general explanation of how private nutritional blood testing fits within broader health assessment, see our Private Blood Tests in London booking guide.
Should Zinc Be Checked With Other Nutrients?
Sometimes.
It depends on why testing is being performed.
Someone with a very restricted diet, malabsorption or unexplained nutritional abnormalities may need a broader assessment than zinc alone.
Relevant markers can include:
iron and ferritin,
vitamin B12,
folate,
vitamin D,
magnesium,
copper,
and other tests selected according to the clinical circumstances.
But ordering every vitamin and mineral available is not automatically better.
Targeted testing reduces the risk of incidental findings that have little clinical relevance.
What Happens After a Low Zinc Result?
The appropriate next step depends on how low the result is and why it may have occurred.
Low Zinc With Poor Dietary Intake
Dietary assessment may help determine whether zinc intake or bioavailability is inadequate.
Low Zinc With Gastrointestinal Symptoms
Malabsorption or ongoing gastrointestinal losses may need investigation.
Simply supplementing zinc without addressing the digestive problem may not correct the underlying cause.
Low Zinc During Acute Illness
Because inflammation can reduce circulating zinc, repeat testing after recovery may sometimes be more informative.
Low Zinc With Other Nutritional Abnormalities
A broader nutritional assessment may be appropriate, particularly where diet, malabsorption or chronic disease could affect several nutrients simultaneously.
Low Zinc While Already Taking Supplements
The result deserves careful interpretation.
Dose, formulation, adherence, timing of the supplement and absorption may all need consideration.
Increasing the dose automatically is not always the correct response.
Should You Take Zinc Supplements Before Testing?
Recent supplementation can affect circulating zinc.
If the purpose of testing is to assess baseline zinc status, taking a zinc supplement immediately before the blood sample can make interpretation more difficult.
London Blood Tests generally advises avoiding vitamin and mineral supplements for around 24–48 hours before nutritional blood testing where appropriate, unless the supplement has been medically prescribed or different instructions have been given.
Do not stop prescribed treatment without medical advice.
The laboratory's specific preparation requirements should always take priority.
What Does the London Blood Tests Zinc Test Include?
The London Blood Tests Zinc Blood Test measures one biomarker:
Zinc
The current listed price is £88, excluding the applicable sample-collection charge.
The listed laboratory turnaround is approximately 1–2 days.
Blood collection is available through clinic appointments or home phlebotomy.
A standalone zinc measurement may be suitable when zinc itself is the specific biomarker required.
For broader nutritional investigation, the Nutritional Health Profile includes zinc alongside vitamins, iron markers, magnesium and other health measurements.
For intracellular mineral assessment, the Mineral Screen (Whole Blood) includes red-cell zinc with seven additional minerals.
The larger panel is not automatically the better choice.
The appropriate test is the one that addresses the reason for investigation.
Private Zinc Blood Testing in London
London Blood Tests provides private zinc blood testing in London with clinic and home collection options.
The standalone Zinc Blood Test measures zinc directly and currently has a listed turnaround of approximately 1–2 days.
A Red Cell Zinc Test is also available where intracellular zinc has specifically been requested.
Where several nutritional markers need to be considered together, the Nutritional Health Profile provides a broader assessment.
For multiple intracellular minerals, the Mineral Screen (Whole Blood) includes red-cell zinc alongside magnesium, selenium, copper and other minerals.
Private testing can make access to laboratory investigations more convenient.
But a zinc result still needs to be interpreted according to symptoms, diet, supplementation, inflammation, sample timing and wider medical history.
Frequently Asked Questions About Zinc Blood Tests
What does a zinc blood test show?
A zinc blood test measures the concentration of zinc in a blood sample and can help assess whether circulating zinc is abnormally low or high.
What is a zinc deficiency test?
A zinc deficiency test generally refers to laboratory measurement of zinc, usually in serum or plasma, to help assess suspected inadequate zinc status.
Can a blood test detect zinc deficiency?
Yes, a low serum or plasma zinc concentration can support a diagnosis of zinc deficiency. However, the measurement has limitations and needs to be interpreted alongside symptoms, diet, inflammation and other risk factors.
What are the symptoms of low zinc?
Low zinc can be associated with impaired wound healing, changes in taste or smell, poor appetite, hair loss, skin problems and impaired immune function. These symptoms are not specific to zinc deficiency.
Does zinc deficiency cause hair loss?
Zinc deficiency can contribute to hair loss, but hair loss has many other possible causes. Zinc testing should therefore be interpreted alongside other relevant investigations.
Can inflammation lower zinc levels?
Yes. Serum or plasma zinc can fall during infection and inflammation, which can complicate interpretation of a low result.
Does the time of day affect zinc levels?
Yes. Zinc concentrations show diurnal variation and can also change after meals.
Do you need to fast for a zinc blood test?
Some laboratories recommend a fasting morning sample because food can influence circulating zinc. Follow the specific instructions supplied for your test.
Is zinc included in a routine blood test?
Usually not. Zinc normally needs to be specifically requested or included within a nutritional or mineral panel.
Can too much zinc be harmful?
Yes. Excessive long-term zinc supplementation can cause side effects and interfere with copper absorption, potentially leading to copper deficiency.
Can zinc supplements affect the blood-test result?
Yes. Recent supplementation may alter circulating zinc and should be considered when the result is interpreted.
Is red-cell zinc better than serum zinc?
Not universally. Red-cell zinc measures a different compartment and may provide additional information in selected circumstances, but no single zinc test perfectly measures total-body zinc status.
What other tests may be useful with zinc?
Depending on the reason for testing, copper, iron studies, vitamin B12, folate, vitamin D, magnesium and other nutritional markers may provide additional information.
The Bottom Line
A zinc blood test can provide useful evidence when zinc deficiency or excess is genuinely suspected.
But zinc is a sensitive biomarker.
Food intake, timing, inflammation, illness, supplementation and even sample collection can influence the result.
That means a low value should not automatically be interpreted as proof that every symptom is caused by zinc deficiency.
Equally, a result within the laboratory reference interval does not provide a perfect measurement of every zinc store in the body.
Serum or plasma zinc remains a practical and widely used clinical assessment.
Alternative measurements such as red-cell zinc examine a different blood compartment, but they should not automatically be described as universally superior.
For private testing in London, London Blood Tests offers a standalone Zinc Blood Test, a Red Cell Zinc Test, the broader Nutritional Health Profile and a Mineral Screen (Whole Blood) where several intracellular minerals are relevant.
The goal is not simply to find a low number and start supplementation.
It is to determine whether zinc imbalance genuinely explains part of the clinical picture and, where it does, why that imbalance has occurred.
Independent Medical Sources
NIH Office of Dietary Supplements — Zinc for Health Professionals
Newcastle Hospitals — Zinc, Serum
Cambridge University Hospitals — Zinc Laboratory Test Information