What Is Zinc Deficiency?

According to the Japanese Society of Clinical Nutrition guideline (2018), zinc deficiency is diagnosed based on symptoms caused by a lack of zinc and the level of zinc in the blood (serum zinc).

Some people have low blood zinc without clear symptoms. This state is called marginal (latent) zinc deficiency.

The guideline lists the following as the main symptoms and findings of zinc deficiency.

These symptoms can also be caused by other diseases, and ruling them out is one of the guideline’s diagnostic criteria. If you have symptoms that concern you, please consult a medical institution rather than judging for yourself.

The guideline classifies serum zinc levels as follows.

Because blood zinc changes during the day, the guideline recommends measuring it in the early morning on an empty stomach.

The diagnosis is not based on blood values alone; it combines symptoms, ruling out other diseases, the serum zinc level, and improvement of symptoms with zinc supplementation.

The guideline groups the causes of zinc deficiency into low intake, poor absorption, increased need and increased loss.

• People at risk: older adults, pregnant women, babies born with low birth weight
• Diet: low food intake (undernutrition), diets low in animal protein, excess phytic acid or dietary fiber (which block zinc absorption)
• Diseases: chronic liver disease (chronic hepatitis, cirrhosis), inflammatory bowel disease, short bowel syndrome, diabetes, chronic kidney disease
• Medication and feeding: long-term use of drugs with a chelating effect, and intravenous or tube feeding with insufficient zinc

For older adults, the guideline names low intake, reduced digestion and absorption, the many lifestyle-related diseases that often accompany zinc deficiency, and medication. Blood zinc levels in older adults are covered in Zinc in Older Adults.

A study of 13,100 patients aged 20+ whose blood zinc was measured at hospitals across Japan (2019–2021) found that the share with zinc deficiency (under 60 μg/dL) rose from 16.3% in their 20s to 45.8% at 80+. Only 11.9% of those aged 80+ were in the normal range (80 μg/dL or more). These are hospital patients, not the general population.

Zinc is abundant in seafood, meat, nuts and seeds, and dairy products, and the basis is getting it from everyday meals. See What Is Zinc? for amounts in foods and recommended daily intake.

If you have symptoms and are concerned about zinc deficiency, you can have a blood test at a medical institution. Treatment for diagnosed deficiency is decided by a doctor. Taking large amounts of zinc continuously, such as from supplements, can cause copper deficiency and anemia, so avoid excess intake.