From the Guidelines
Low iron levels and low ferritin levels are two distinct indicators of iron status in the body, with ferritin being a more reliable marker of iron deficiency, as it reflects the body's iron storage capacity. Iron levels refer to the amount of iron currently circulating in your bloodstream, which can fluctuate throughout the day based on recent meals and other factors 1. Ferritin, however, measures your body's iron storage capacity and provides a more accurate picture of your long-term iron status.
Key Differences
- Low iron levels indicate an immediate deficiency in circulating iron, which may cause symptoms like fatigue but doesn't necessarily mean your iron stores are depleted.
- Low ferritin levels indicate that your body's iron reserves are depleted, suggesting a more chronic iron deficiency that has progressed to the point where your storage capacity is compromised.
Diagnosis and Treatment
According to the British Society of Gastroenterology guidelines, serum ferritin is the single most useful marker of iron deficiency anaemia (IDA), and a good response to iron therapy is highly suggestive of absolute iron deficiency, even if the results of iron studies are equivocal 1. Treatment for either condition usually involves iron supplementation, and the duration of treatment may be longer for low ferritin to adequately replenish stores.
Clinical Considerations
In clinical practice, distinguishing between absolute and functional iron deficiency is crucial, as functional iron deficiency may occur despite normal or elevated serum ferritin levels, particularly in patients receiving Epoetin therapy 1. Therefore, it is essential to consider both iron and ferritin levels, as well as the clinical context, when diagnosing and managing iron deficiency.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Difference between Iron and Ferritin in Lab Tests
- Iron and ferritin are two related but distinct measures of iron status in the body.
- Iron is an essential mineral that plays a crucial role in various bodily functions, including oxygen transport and energy production.
- Ferritin, on the other hand, is a protein that stores iron in the body, and its levels are used as an indicator of iron stores 2, 3.
Low Iron Levels vs. Low Ferritin Levels
- Low iron levels (iron deficiency) occur when the body does not have enough iron to meet its needs, often due to inadequate dietary intake, increased requirements, or chronic blood loss.
- Low ferritin levels, specifically, indicate depleted iron stores in the body, which can be a sign of iron deficiency anemia 3, 4.
- A study found that reticulocyte hemoglobin (RET-He) and serum ferritin are both markers of bone marrow iron store in iron deficiency anemia, but RET-He was a better predictor of bone marrow iron stores than serum ferritin 4.
Clinical Implications
- Low ferritin levels are a highly specific and sensitive marker for diagnosing iron deficiency, especially in patients with hair loss or other symptoms of iron deficiency 2.
- Elevated ferritin levels, on the other hand, can indicate iron overload or inflammation, and may be associated with various diseases, including malignant conditions 5.
- Intravenous iron therapy has been shown to improve exercise tolerance and symptoms in patients with chronic heart failure and iron deficiency, regardless of anemia status 6.
Diagnostic Thresholds
- The diagnostic accuracy of ferritin concentrations for detecting iron deficiency and overload has been evaluated in various studies, with thresholds ranging from 12 to 200 µg/L for iron deficiency and varying levels for iron overload 3.
- A study found that a ferritin threshold of 30 μg/L had a sensitivity of 79% and specificity of 98% for diagnosing iron deficiency in non-healthy adults 3.