When to Order Iron Studies (Iron, TIBC, Ferritin)
Order iron studies (including iron, TIBC, and ferritin) at any level of anemia when iron deficiency is suspected, rather than waiting for a specific hemoglobin threshold. 1
Hemoglobin Thresholds for Investigation
The decision to order iron studies should be based on the presence of anemia combined with clinical suspicion of iron deficiency, not a specific hemoglobin cutoff:
- Men: Investigate when hemoglobin falls below 13 g/dL (or below your laboratory's lower limit of normal) 1
- Non-pregnant women: Investigate when hemoglobin falls below 12 g/dL (or below your laboratory's lower limit of normal) 1
- Pregnant women: Investigate when hemoglobin falls below 11 g/dL 1
Priority Investigation Thresholds
More urgent investigation is warranted at lower hemoglobin levels, as these suggest more serious underlying disease:
- Men with Hb <12 g/dL: Requires more urgent investigation 1
- Postmenopausal women with Hb <10 g/dL: Requires more urgent investigation 1
However, any level of anemia should be investigated in the presence of iron deficiency, as even mild anemia can indicate significant pathology, particularly gastrointestinal malignancy in men and postmenopausal women. 1
Essential Iron Studies to Order
When ordering iron studies, obtain a complete iron panel including:
- Serum ferritin (the single most useful marker of iron deficiency) 1, 2
- Serum iron 1
- Total iron-binding capacity (TIBC) 1
- Transferrin saturation (calculated as serum iron/TIBC × 100) 1
Ferritin is the most reliable single test, but other markers help when ferritin may be falsely normal due to inflammation or chronic disease. 1
Diagnostic Thresholds for Iron Deficiency
- Ferritin <45 ng/mL: Indicates iron deficiency 2
- Transferrin saturation <16%: Suggests iron deficiency in the general population 1
- Transferrin saturation <20%: Threshold used in chronic kidney disease patients 1
Important Clinical Caveats
Do not wait for severe anemia to order iron studies. Early detection of iron deficiency allows for:
- Identification of underlying causes (especially GI blood loss or malignancy) 1
- Prevention of progression to severe anemia 1
- Earlier treatment initiation 1
Ferritin can be falsely elevated in inflammatory states, chronic disease, or malignancy, so consider additional iron markers (transferrin saturation, TIBC) when clinical suspicion remains high despite normal ferritin. 1
Red cell indices provide clues: Look for microcytosis (low MCV) and hypochromia (low MCH), though these may be absent in early iron deficiency or masked by concurrent conditions. 1