Serum zinc reference ranges
| Group | Normal Range | Notes |
|---|---|---|
| Adults (fasting AM sample) | 70–120 mcg/dL (10.7–18.4 µmol/L) | Levels are highest in the morning before eating |
| Mild deficiency | 60–70 mcg/dL | Subtle symptoms — fatigue, reduced immunity |
| Moderate deficiency | 40–60 mcg/dL | Hair loss, skin problems, poor wound healing |
| Severe deficiency | <40 mcg/dL | Growth retardation, hypogonadism, acrodermatitis |
Why zinc levels are tricky to measure
Important caveats for serum zinc
Serum zinc only captures about 0.1% of total body zinc — most zinc is inside cells. Serum levels fall during infections, inflammation and stress even when body stores are adequate (zinc is redistributed). For this reason, a normal serum zinc does not absolutely rule out deficiency, and levels should always be interpreted alongside symptoms and risk factors. Levels are highest in the morning before eating, so samples should be collected fasting in the morning for best accuracy.
Symptoms of zinc deficiency
| Symptom | Why it happens |
|---|---|
| Hair loss (telogen effluvium) | Zinc is required for hair follicle function and cell division |
| Poor wound healing | Zinc activates collagen synthesis enzymes |
| Loss of taste and smell (ageusia/anosmia) | Zinc-dependent enzymes in taste buds and olfactory neurons |
| Frequent infections | Zinc is essential for T-cell immune function |
| White spots on nails (leukonychia) | Classically associated with zinc deficiency |
| Acne and slow-healing skin | Zinc regulates oil glands and has anti-inflammatory properties |
| Reduced fertility (men) | Zinc is concentrated in sperm and needed for testosterone production |
Who is at risk of zinc deficiency?
High-risk groups
Vegetarians and vegans (plant zinc is less bioavailable than meat zinc due to phytates); older adults (reduced absorption and dietary intake); people with inflammatory bowel disease, coeliac disease or short bowel syndrome; chronic alcohol users (alcohol impairs zinc absorption and increases urinary excretion); pregnant and breastfeeding women (increased demand); people on long-term medications including diuretics, ACE inhibitors and some antacids.
Zinc and immune function
Zinc is one of the most studied micronutrients for immunity. It is essential for the development and activation of T-lymphocytes, natural killer cells, and neutrophils. Even mild zinc deficiency reduces immune response. Zinc lozenges are widely studied for reducing the duration of common colds — evidence suggests they work best when taken within 24 hours of symptom onset.
Questions to ask your doctor
- Should my zinc be tested fasting in the morning for accuracy?
- Could my hair loss or poor wound healing be zinc-related?
- Do I need zinc supplementation, and what dose is safe?
- Does my diet or medication affect zinc absorption?