Zinc Levels Explained: Low Zinc, Symptoms and Testing

Zinc is a trace mineral your body uses to make new cells and enzymes, to process the carbohydrate, fat and protein in food, and to heal wounds. It also supports your immune system. Your body cannot store much zinc, so it relies on a steady supply from foods such as meat, shellfish, cheese and other dairy foods, bread and cereal products.

A zinc blood test is often requested for hair loss, slow-healing skin, frequent infections or a restrictive diet, and to check people who take zinc supplements. This guide explains the usual range, why infection, time of day and meals can change the result, the common causes and symptoms of low zinc, how serum and red cell zinc differ, and the safe limit for supplements.

Test it in Chiswick: our Zinc blood test costs £79, with your result explained in person by a practitioner. No GP referral needed. Book this test or call 020 4515 0000.

Quick answer

Many UK laboratories use an adult serum zinc range of roughly 10 to 20 µmol/L, although some set the upper limit nearer 24 or 25 µmol/L. A level below about 7 µmol/L suggests a true deficiency. Borderline low results are common and harder to read, because zinc falls during infection or inflammation, after meals and when albumin is low. Low zinc can cause hair loss, poor wound healing, skin rashes and more infections. The NHS advises taking no more than 25 mg of zinc supplements a day unless a doctor advises it, because high doses reduce copper absorption.

What a zinc blood test measures

The standard test measures zinc in serum, the liquid part of your blood. Only a small share of your body's zinc is found there, and most of it travels attached to albumin, the main protein in blood. That is why laboratories advise reading a zinc result alongside albumin: if albumin is low, zinc will usually be low too, even when your zinc intake is fine.

Serum zinc or red cell zinc?

Our Zinc test (£79) measures serum zinc, the test used by NHS laboratories and the one UK guidance is based on. Our Red Cell Zinc test (£99) measures the zinc held inside red blood cells, which contain around ten times more zinc than the same amount of serum. It is sometimes used as a possible longer-term view of zinc status, because it is thought to be less affected by a recent meal or a short illness.

Red cell zinc is not used routinely in NHS practice, there is no agreed UK guidance on acting on it, and ranges differ more between laboratories. For most people, serum zinc read alongside albumin is the right first test. Your practitioner can help you decide whether a red cell test would add anything.

What can affect your zinc result

• Infection and inflammation: zinc is a negative acute phase reactant, which means the blood level drops during illness, injury or surgery. One NHS laboratory advises measuring zinc two weeks after an acute illness has settled, and another suggests checking CRP, a marker of inflammation, at the same time.
• Time of day: zinc rises and falls through the day in healthy people. One NHS laboratory notes a peak around 10am.
• Meals: blood zinc falls after eating, so a morning sample taken before breakfast is often preferred.
• Low albumin: common with illness, liver disease and some kidney conditions, and it pulls zinc down with it.
• Pregnancy and some medicines: both can change zinc levels.
• Sample handling: zinc is present in some tube stoppers and gels, which can make a result falsely high. One NHS laboratory found results from gel tubes were typically 2 to 4 µmol/L higher. Damaged (haemolysed) samples are also unsuitable, because zinc leaks out of red cells.

What your result means

• Very low (below about 7 µmol/L): NHS laboratory guidance says this suggests a marked deficiency. Your GP will want to find the cause and may suggest treatment.
• Borderline low (about 7 to 10 µmol/L): common and often not significant on its own. It may reflect a recent infection, low albumin or a sample taken after a meal. A repeat test in the morning, before eating and once you are well, is often the next step.
• Within range (about 10 to 20 µmol/L): your blood level is where it is expected to be. If symptoms continue, other causes are worth exploring.
• High (above the laboratory range): usually linked to supplements or to contamination of the sample. One NHS laboratory notes that levels above 40 µmol/L may harm the kidneys.

These are typical adult values. Ranges vary between laboratories, so compare your result with the range printed on your own report.

Symptoms of low zinc

Mild low zinc often causes no obvious symptoms. When deficiency is more marked, it can cause:

• hair loss or thinning hair
• wounds that heal slowly
• dry, inflamed or scaly skin (dermatitis)
• more frequent infections, because the immune system works less well

All of these have many other causes, so a low zinc result is one piece of the picture rather than an answer on its own.

Common causes of low zinc

• Low intake: diets with little meat, shellfish or dairy, or a poor appetite.
• Poor absorption: conditions such as coeliac disease and Crohn's disease, long-lasting diarrhoea, or weight loss surgery.
• Higher needs: pregnancy, burns and recovery from serious illness, when the body needs more zinc than it takes in.
• Alcohol: regular heavy drinking is linked to low zinc.
• Rare inherited conditions: such as acrodermatitis enteropathica, which affects how zinc is absorbed.

Remember that infection, inflammation and low albumin can make zinc look low without a true shortage.

Zinc supplements: how much is safe?

The NHS says adults aged 19 to 64 need about 9.5 mg of zinc a day (men) or 7 mg a day (women), and most people get this from a varied diet. The NHS advises: do not take more than 25 mg of zinc supplements a day unless advised to by a doctor.

The main reason is copper. Taking high doses of zinc reduces the amount of copper your body can absorb, and over time this can lead to copper deficiency, anaemia and weakening of the bones. Very high doses can also cause nausea, vomiting and drowsiness and may affect the kidneys. Zinc often appears in multivitamins, immune support products and cold remedies, so add up what you take from every source. If you take high-dose zinc on medical advice, your doctor may also check your copper level.

When to see your GP or get urgent help

Call NHS 111 or go to A&E if you have swallowed a large amount of zinc supplements, or if a slow-healing wound becomes hot, swollen or very painful and you feel unwell or feverish.

Book a GP appointment if you have a very low result, ongoing diarrhoea, unexplained weight loss, blood in your poo, or signs of a malabsorption condition. Also see your GP if you have taken more than 25 mg of zinc a day for a long time and feel tired or breathless, as these can be signs of anaemia.

Who should consider a zinc test

• People with hair loss, slow wound healing, skin rashes or frequent infections
• People with coeliac disease, Crohn's disease, long-lasting diarrhoea or previous weight loss surgery
• People on a restrictive diet, or with a history of heavy drinking
• Anyone who has taken zinc supplements above 25 mg a day for months

Preparing for the test

Book a morning appointment if you can, and come before breakfast, drinking water as normal. If you have had an infection or an operation recently, ask whether to wait until you have recovered. Tell us about any zinc, multivitamin or immune supplements and when you last took them, so your result can be read correctly.

How often to retest

A borderline low result is often repeated once you are well, in the morning and before eating. If you are treated for a deficiency, your GP or practitioner will advise when to recheck. If your result is in range and you have no ongoing risk factors, regular testing is not usually needed.

Frequently asked questions

Is a zinc level of 9 µmol/L low?

It is slightly below many UK laboratory ranges, but a result like this is common and often not significant on its own. It is worth checking albumin and whether you were unwell or had eaten, and repeating the test in the morning before breakfast.

Can a cold or infection lower my zinc level?

Yes. Zinc falls in the blood during infection and inflammation, so a low result while you are unwell may not mean you are deficient. One NHS laboratory suggests testing about two weeks after you have recovered.

Do I need to fast for a zinc blood test?

It helps. Zinc falls after meals, so a morning sample before breakfast gives a result that is easier to compare with the range.

How much zinc is too much?

The NHS advises no more than 25 mg a day from supplements unless a doctor advises otherwise. Long-term higher doses can lower copper and lead to anaemia and weaker bones.

Is red cell zinc better than serum zinc?

Not for most people. Serum zinc is the standard NHS test. Red cell zinc may give a longer-term view, but it is not used routinely and has no agreed UK guidance.

Zinc testing in Chiswick

We take your sample at our clinic at 8 to 9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ. We are a short walk from Turnham Green station (District line, with Piccadilly line trains stopping there early morning and late evening only) and close to the 94, E3 and 272 bus routes. Limited parking is available on request when you book. Your sample is analysed at the Randox accredited laboratory, no GP referral is needed, and most results are ready within a few working days. A practitioner explains your result with you in person, and a GP feedback report is available on request.

Book the Zinc blood test on its own, or choose the Vitamins and Minerals Check (£99), which reports zinc alongside albumin, iron studies, vitamin D, vitamin B12, folate, magnesium and calcium. You can also compare every blood test and price, or read our guides to blood tests for hair loss and blood tests for frequent infections.

This article is general information, not medical advice. Discuss your results with your GP or practitioner.