Zinc: what it is, what it tells you and when it’s tested

Zinc is a mineral your body uses in many processes: immune defences, wound healing, skin, taste and smell. Your body keeps no real store of it, so you need a little every day from food. The test measures zinc in your blood, which is only a small part of what you have.

When it’s tested

Doctors order it when they suspect a shortage: for example with a condition that reduces absorption, such as coeliac or Crohn’s disease, after bowel or stomach surgery, with lasting diarrhoea, heavy drinking or a very restricted diet. They also ask for it if you have taken high-dose zinc for a long time.

For people who feel well it is not a useful test. Blood zinc changes with meals, the time of the draw and inflammation, and says little about how much zinc your body really holds. It works better for studying a population than for judging one person.

That is why Rosa does not test it. Instead it looks at CRP, which shows whether inflammation could be lowering it, albumin, which carries it in the blood, and a blood count, which shows the harm of too much.

What it tells you, and what it does not

If it is low, there may be a shortage. But often inflammation, a recent meal or an afternoon blood draw is behind it.

It does not show how much zinc is inside your cells, where almost all of it sits. That is why your doctor reads it with your symptoms and what you eat.

If it is high, you almost always take a supplement, or the sample was contaminated.

That is why it is read together with other tests:

Normal zinc levels

The lab decides what is normal. Some reports use µg/dL, others µmol/L, with different numbers. The range printed next to your result is what counts.

As a guide, the thresholds used in studies count as low, in the morning and fasting, a value below 70 µg/dL in women and below 74 in men. After a meal and in the afternoon zinc is naturally lower, so the thresholds drop.

Pregnancy and the pill lower it a little too. A single slightly low value without symptoms is usually not enough to call it a shortage.

If your zinc is low or high

What causes low or high zinc

Blood zinc depends on what you eat, but also on how and when the blood is taken.

Symptoms of zinc deficiency

A real shortage can show in different ways. For example:

These signs are not specific: they can have many other causes. If you have them, talk to your doctor.

Zinc and supplements: when it is too much

Zinc is in many supplements. If you take high doses for months, your body absorbs less copper.

A lack of copper can cause anaemia, low white cells and, in more serious cases, nerve problems, with tingling and trouble walking. It usually recovers once you stop.

So before taking zinc for a long time, ask your doctor whether you need it and how much.

What can skew the result

Blood zinc is a delicate test. Many things shift it.

When to worry

Talk to your doctor if:

Frequently asked questions

What are normal blood zinc levels? It depends on the lab and the unit. The thresholds used in studies, in the morning and fasting, count as low a value below 70 µg/dL in women and below 74 in men. The range on your report is what counts.

What are the symptoms of zinc deficiency? Weaker taste and smell, slow-healing wounds, skin rashes, hair loss and frequent infections. These signs are not specific: show them to your doctor.

Do I need to fast for a zinc test? Yes. A morning draw after at least eight hours of fasting is best, because meals and the time of day change the value.

Is low zinc always about what I eat? No. Often inflammation, a recent meal or an afternoon draw is behind it. A real shortage is looked for with your doctor, taking your symptoms into account.

Does Rosa test zinc? No. Rosa measures CRP, albumin and a full blood count, which help read what shifts zinc or the harm of too much. If your doctor wants zinc, they order it separately.

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