WHAT DISEASES CAUSE LOW FERRITIN?

Low ferritin levels are a common finding on blood tests and often raise questions about iron stores and overall health. Ferritin reflects how much iron your body has stored, and when levels are low, it can point to underlying medical conditions rather than diet alone. 

Understanding the possible causes is important, especially if symptoms such as fatigue, breathlessness, or frequent infections are present. A simple blood test such as a ferritin check can help identify whether low iron stores may be contributing to how you feel, and whether further investigation is needed. If you are concerned about your iron levels, a ferritin blood test can provide clear insight into your body’s iron reserves.

Ferritin is a protein that stores iron inside your cells and releases it when your body needs it. Because iron is essential for making healthy red blood cells, low ferritin often develops before iron deficiency anaemia appears. This means ferritin is usually one of the earliest markers of iron depletion.

Low ferritin does not always cause symptoms at first, but over time it can lead to tiredness, weakness, headaches, hair thinning, pale skin, and reduced exercise tolerance. When ferritin levels drop, doctors often look beyond diet to check whether an underlying condition is affecting iron absorption, storage, or blood loss.

Iron deficiency anaemia is the most common condition linked to low ferritin. It occurs when iron stores become so depleted that the body can no longer produce enough healthy red blood cells. In many cases, low ferritin appears first, followed later by changes in haemoglobin levels.

Iron deficiency anaemia may develop due to ongoing blood loss, poor absorption of iron, or increased iron requirements. Symptoms can include persistent fatigue, shortness of breath, dizziness, and palpitations. Identifying the cause of iron loss is essential to prevent recurrence.

Several digestive system disorders can cause low ferritin by interfering with iron absorption or causing slow blood loss.

Conditions such as coeliac disease damage the lining of the small intestine, reducing the body’s ability to absorb iron from food. Inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis, may cause both malabsorption and chronic intestinal bleeding.

Stomach ulcers, gastritis, and bowel polyps can also lead to gradual blood loss that may go unnoticed, resulting in falling ferritin levels over time. 

Bowel cancer can also cause blood loss from the gut so doctors will often screen for bowel cancer in patients with a low ferritin, particularly in men and post-menopausal women.

In women of reproductive age, heavy or prolonged menstrual bleeding is one of the most common causes of low ferritin. Conditions such as fibroids, endometriosis, or hormonal imbalances can significantly increase monthly blood loss.

Pregnancy also increases iron requirements, as iron is needed to support both maternal blood volume and fetal development. Without adequate intake or supplementation, ferritin levels can fall quickly.

Chronic kidney disease can contribute to low ferritin through several mechanisms. Reduced kidney function may affect the production of erythropoietin, a hormone involved in red blood cell production. In addition, inflammation associated with kidney disease can alter iron handling in the body.

People with kidney disease may develop low ferritin even if their iron intake appears adequate, making blood testing particularly important in this group.

Rarely, low ferritin is due to blood loss in the urinary tract (e.g. the bladder or the kidneys). This can be a sign of a sinister diagnosis such as bladder cancer so, when ferritin is low, doctors will often check a urine sample for the presence of microscopic blood.

Underactive thyroid function can be associated with low ferritin levels. Hypothyroidism may slow digestion and reduce stomach acid production, which can impair iron absorption.

Low ferritin may also worsen symptoms of thyroid disease, such as fatigue, cold sensitivity, and hair thinning, creating a cycle where both conditions influence each other.

Long term inflammatory conditions can disrupt how iron is stored and used. Diseases such as rheumatoid arthritis, lupus, and chronic infections may cause iron to become trapped in storage sites, reducing circulating ferritin levels.

Although inflammation can sometimes cause ferritin to rise, certain autoimmune or inflammatory states may still lead to functional iron deficiency, especially if dietary intake is low.

Low ferritin may also occur in people whose diets lack sufficient iron or who follow restrictive eating patterns. Vegetarian or vegan diets can be healthy, but plant based iron is less easily absorbed than iron from animal sources.

Conditions that reduce stomach acid or long term use of certain medications can also interfere with iron absorption, even when dietary intake seems adequate.

If low ferritin is suspected or symptoms persist, a blood test can help confirm iron status and guide further investigation. Identifying the underlying cause is essential, as simply increasing iron intake may not be enough if an underlying condition is present.

A ferritin blood test can help determine whether iron stores are low and whether additional testing or medical review may be appropriate.