A low ferritin level indicates that the body’s iron reserves are depleted. Ferritin is a protein that stores iron, and low levels are a reliable sign of iron deficiency. While a search for low ferritin may prompt concern about cancer, the vast majority of cases are caused by common, manageable conditions, such as dietary deficiency or chronic blood loss. Understanding ferritin’s function clarifies why it is a marker for iron status, rather than a primary marker for malignancy.
What Ferritin Is and Its Role in the Body
Ferritin functions as the body’s primary iron storage system, acting as a warehouse for the iron not immediately needed for oxygen transport. This protein is predominantly located inside cells, particularly in the liver, spleen, and bone marrow. It safely sequesters iron, holding it in a non-toxic, readily available form until the body requires it for processes like red blood cell production.
A small amount of ferritin circulates in the bloodstream, and measuring this serum ferritin provides an indirect, yet accurate, reflection of the total iron stored throughout the body. The test is a simple blood draw and is considered the most sensitive indicator for diagnosing iron deficiency, often showing a drop before other iron-related measures change. Standard reference ranges for ferritin vary, but levels below 30 nanograms per milliliter in adults are indicative of depleted iron stores.
The Primary Reasons for Low Ferritin Levels
The most frequent cause of low ferritin is a state of negative iron balance, where iron loss or demand exceeds intake and absorption. When the body exhausts its ferritin stores and can no longer produce enough healthy red blood cells, Iron Deficiency Anemia (IDA) develops. IDA is the most common form of anemia globally and is the primary reason for a low ferritin result.
Chronic, subtle blood loss is a major mechanism leading to low ferritin, often occurring without the person’s immediate awareness. For premenopausal women, heavy menstrual bleeding is a common cause of iron depletion. In both men and postmenopausal women, chronic occult bleeding from the gastrointestinal (GI) tract is the most frequent source of blood loss. This GI bleeding can be due to benign issues like peptic ulcers, hemorrhoids, or chronic non-steroidal anti-inflammatory drug (NSAID) use.
Other factors relate to insufficient intake or impaired absorption of dietary iron. People who follow vegetarian or vegan diets may have lower intake of easily absorbed heme iron found in meat, leading to reduced stores. Conditions that affect the digestive lining, such as celiac disease or inflammatory bowel disease, can impair the gut’s ability to absorb iron. Surgical procedures like bariatric surgery also commonly interfere with normal iron absorption pathways.
Understanding Low Ferritin in the Context of Cancer
While low ferritin is not a primary cancer marker, a significant drop can be an indirect sign of a malignancy, particularly those affecting the digestive system. Cancer can cause low ferritin by inducing chronic, low-level blood loss that gradually depletes the body’s iron reserves. Gastrointestinal cancers, such as those in the stomach, colon, or small bowel, are known to bleed subtly over time, leading to iron deficiency anemia.
High ferritin levels are more commonly associated with cancer due to the inflammatory state many tumors create. Ferritin acts as an acute-phase reactant, meaning its level rises during inflammation and infection, which can mask an underlying iron deficiency. Therefore, a low ferritin result in a patient suspected of having cancer often points specifically to an iron-losing process, such as internal hemorrhage, rather than inflammation.
Low ferritin signals that the cancer or its effect on the body is causing a constant loss of iron. This iron deficiency state can also be exacerbated by cancer treatments or by a tumor interfering with the body’s iron utilization. When low ferritin is discovered in men or postmenopausal women, the possible presence of a GI malignancy must always be investigated as a potential cause of occult bleeding.
Steps Following a Low Ferritin Result
A low ferritin result necessitates a focused investigation to identify the source of iron depletion. The initial step is usually a broader iron panel, which includes tests like a Complete Blood Count (CBC) and transferrin saturation. The CBC reveals if the low iron has progressed to anemia, while transferrin saturation measures the percentage of iron-carrying protein that is bound to iron.
If the cause is not immediately apparent, such as heavy menstruation or dietary restriction, the investigation focuses on ruling out occult blood loss. A test for fecal occult blood may be ordered to check for microscopic amounts of blood in the stool. For men and postmenopausal women with unexplained iron deficiency, a thorough examination of the gastrointestinal tract is often required.
This GI investigation involves an upper endoscopy and a colonoscopy to visually inspect the esophagus, stomach, and colon for sources of bleeding, such as ulcers, polyps, or tumors. If those initial procedures are normal and the iron deficiency persists, further imaging or a capsule endoscopy may be used to examine the small bowel. The management plan involves not only treating the iron deficiency with supplements but also addressing the underlying cause to prevent further iron loss.