Zinc
Zinc is a mineral your body cannot make, so you need it from food. It matters for your immune system, your skin and wound healing, and normal growth. A blood test gives a rough guide to your zinc, but it can miss a mild shortfall — so a normal result is reassuring without being the whole story, and your GP reads it with your symptoms and diet.
Standard CareWhat is zinc?
Zinc is a mineral that helps your cells grow and divide. Your body cannot make zinc, so you need to get it from the food you eat. It plays a central role in fighting off infection — supporting the immune cells that respond when you are unwell — and in maintaining healthy skin, hair and the lining of your gut. Zinc is also involved in wound healing and in the normal senses of taste and smell. The blood test measures the amount of zinc circulating in your plasma or serum. It is a useful starting point, but it has a known limitation: your zinc level shifts a lot through the day, with meals, and with infection or inflammation — so even a normal reading does not completely rule out a mild shortfall.
Why is it tested?
Your GP may order a zinc test if you have symptoms that could fit deficiency — things like skin changes (a rash or slow-healing sores), hair loss, repeated infections, or poor appetite. It is also sometimes checked in people with conditions that affect absorption, such as coeliac disease or inflammatory bowel disease. One thing worth knowing: the blood test is not very reliable for people with mild zinc deficiency. A result in range does not always mean your stores are adequate, and your GP will weigh the level alongside your symptoms, diet, and any conditions you have.
Reference range (Australia)
There is no separate male/female reference interval for serum zinc. Results vary significantly with the time of day, recent meals, and inflammation — the highest levels are typically seen early in the morning after an overnight fast. Always use the interval on your own report.
Reference intervals vary between laboratories. Always use the range printed on your own report.
What your result means
A lower-than-usual result can point to zinc deficiency, but it can also reflect the natural dip that happens after a meal, during inflammation, or when your body is fighting an infection. A low result on its own is not a diagnosis. Your GP will look at it alongside your symptoms — things like skin changes, hair loss, poor immunity — and your diet to work out what is going on. It is also worth knowing that a normal blood level does not completely rule out mild deficiency, because zinc in the blood is only a fraction of the body's total stores.
A result within the range on your report suggests your circulating zinc is likely adequate, though it cannot fully rule out a mild shortfall. If you have symptoms that prompted the test, it is still worth a conversation with your GP, because mild deficiency can exist even with a normal blood level, and the result is most useful read together with the full picture.
A higher-than-usual zinc level most often reflects recent supplements, a sample taken soon after a zinc-rich meal, or (rarely) contamination during collection. Dietary zinc alone rarely pushes the blood level above range. If you take zinc supplements, mention this to your GP — they can decide whether a repeat test or dose adjustment makes sense.
What can affect your result
Several things shift a zinc result independently of your body's true zinc stores. Meals matter: plasma zinc drops after eating and is highest early in the morning after an overnight fast. If you were not fasted when your blood was taken, the result may read lower than it would otherwise. Inflammation pulls zinc out of the blood as part of the body's acute-phase response — the same shift that affects iron and albumin. So if you were unwell or had any active inflammatory condition at the time of the test, a low reading may reflect that rather than true deficiency. A haemolysed sample (where red blood cells are broken during collection) can falsely raise the result, because zinc is concentrated inside red blood cells. Chronic stress, kidney disease, and conditions that affect gut absorption — such as coeliac disease or inflammatory bowel disease — can genuinely lower zinc over time.
When to act
If your result is low and you have symptoms that fit zinc deficiency — skin changes, hair loss, slow wound healing, or repeated infections — that is worth discussing with your GP. They will consider your diet, any absorption issues, and whether a repeat test (ideally fasted, first thing in the morning) would give a clearer picture. If your result is high and you take zinc supplements, a chat with your GP about dose is sensible — very high zinc over time can interfere with copper absorption. This page is general information and is not a substitute for advice from your GP.
Frequently asked questions
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