Low Ferritin – Causes, Symptoms and Treatment

What Is Low Ferritin?

Ferritin is a protein that stores iron in the body and releases it when needed. The ferritin level measured in the blood is considered the most reliable marker for assessing the body's iron stores. A low ferritin level is diagnosed when the measured concentration falls below the reference range. In adults, values below 12–15 µg/l are generally considered low, although laboratory-specific cut-off values may vary.

A low ferritin level is often the earliest sign of developing iron deficiency, appearing before a full iron deficiency anemia (low red blood cell count due to insufficient iron) becomes evident. Globally, iron deficiency is one of the most common nutritional deficiencies.

Causes

A low ferritin level can result from several different causes:

• Insufficient iron intake: A diet low in iron, or a vegetarian or vegan diet without targeted supplementation.
• Increased iron demand: Pregnancy, breastfeeding, growth phases in children and adolescents, and intensive endurance sports.
• Blood loss: Heavy menstrual bleeding, gastric ulcers, intestinal bleeding, frequent blood donation, or surgical procedures.
• Impaired iron absorption in the intestine: Conditions such as coeliac disease, Crohn's disease, or previous gastric surgery can reduce iron absorption.
• Chronic diseases: Certain kidney conditions or chronic inflammatory diseases can disrupt iron metabolism.

Symptoms

Low ferritin does not always cause immediately noticeable symptoms. Possible signs of iron deficiency include:

• Persistent fatigue and exhaustion
• Paleness of the skin and mucous membranes
• Difficulty concentrating and headaches
• Hair loss and brittle nails
• Shortness of breath during physical exertion
• Restless legs syndrome
• Increased susceptibility to infections

Diagnosis

Low ferritin is diagnosed through a simple blood test. In addition to ferritin, several other blood parameters are commonly measured to obtain a complete picture of iron status:

• Serum iron and transferrin (the iron transport protein)
• Transferrin saturation
• Full blood count (haemoglobin, red blood cells, MCV)
• Soluble transferrin receptor (sTfR)

It is important to note that ferritin is also an acute-phase protein, meaning its levels can be falsely elevated during inflammation, potentially masking an underlying iron deficiency. Results should therefore always be interpreted within the broader clinical context.

Treatment

Dietary Adjustments

For mild iron deficiency, an iron-rich diet may help replenish iron stores. Good dietary sources of iron include red meat, legumes, whole grains, dark leafy vegetables, and nuts. Consuming vitamin C alongside plant-based iron sources significantly improves absorption.

Oral Iron Supplements

When ferritin levels are significantly low or anaemia is already present, oral iron supplements (e.g., ferrous sulphate, ferrous gluconate) are commonly prescribed. They are ideally taken on an empty stomach. Common side effects include gastrointestinal discomfort, constipation, and dark-coloured stools.

Intravenous Iron Therapy

If oral therapy is insufficient or not tolerated — for example, in cases of malabsorption, severe anaemia, or during pregnancy — iron can be administered directly into a vein. This is typically carried out on an outpatient basis under medical supervision.

Treating the Underlying Cause

If a treatable underlying condition is responsible for the low ferritin level (e.g., heavy menstrual bleeding, coeliac disease), addressing that condition is essential for a lasting improvement in iron status.

When to See a Doctor

If you experience persistent fatigue, hair loss, paleness, or other possible symptoms of iron deficiency, you should seek medical advice. A simple blood test can quickly clarify the situation. Self-medicating with high-dose iron supplements without medical evaluation is not recommended, as iron overload can also be harmful.

References

1. World Health Organization (WHO): Guideline: Daily iron supplementation in adult women and adolescent girls. WHO, Geneva, 2016.
2. Camaschella C.: Iron-deficiency anemia. New England Journal of Medicine, 2015; 372(19):1832–1843.
3. Kasper DL et al.: Harrison's Principles of Internal Medicine. 21st edition, McGraw-Hill Education, 2022.