What does a transferrin level of 236 mg/dL indicate?

Transferrin Level of 236 mg/dL: Clinical Interpretation

A transferrin level of 236 mg/dL is within the normal reference range (200-360 mg/dL) and does not indicate iron deficiency on its own—you must interpret this value alongside transferrin saturation, serum ferritin, and inflammatory markers to determine iron status. 1

Understanding the Physiological Context

• Transferrin is the primary iron transport protein, and when iron stores are depleted, the liver produces more transferrin molecules to maximize iron-binding capacity and transport whatever limited iron is available 1
• High transferrin/TIBC (>360 mg/dL) indicates iron deficiency as a compensatory response to low iron stores, while your patient's value of 236 mg/dL falls in the mid-normal range 1
• Transferrin elevation occurs after iron stores are already depleted, making it a less sensitive early marker compared to serum ferritin, which drops first when stores begin to decline 1

Critical Diagnostic Algorithm

Step 1: Calculate transferrin saturation (serum iron/TIBC × 100)

• Transferrin saturation <16-20% confirms inadequate iron availability for erythropoiesis, regardless of the absolute transferrin level 1
• This is more reliable than transferrin/TIBC alone, especially in inflammatory states 1

Step 2: Check serum ferritin with inflammatory context

• In non-inflammatory states: ferritin <30 ng/mL confirms absolute iron deficiency 1
• In inflammatory conditions: use ferritin <100 ng/mL as the threshold because ferritin acts as an acute-phase reactant and can be falsely elevated 2, 1
• The classic pattern of absolute iron deficiency without inflammation is: low serum iron, high TIBC/transferrin (>360 mg/dL), low transferrin saturation (<20%), and low ferritin (<30 ng/mL) 1

Step 3: Assess for confounding factors

• Inflammation, chronic infection, malignancies, liver disease, nephrotic syndrome, and malnutrition can lower TIBC readings despite true iron deficiency, creating false-normal or low results 1
• Oral contraceptive use and pregnancy can raise TIBC readings independent of iron status 1
• In chronic kidney disease patients, TIBC may be lower than in healthy individuals despite true iron deficiency 1

Specific Clinical Scenarios

In liver disease patients:

• Serum ferritin is frequently elevated disproportionately to actual iron stores due to hepatocellular damage and inflammation 3
• Transferrin saturation becomes more reliable than ferritin alone for assessing iron status 3
• In alcoholic liver disease, serum ferritin can be markedly elevated (>1000 mcg/L in 11% of cases) and decreases rapidly with abstinence 3

In inflammatory conditions (IBD, chronic disease):

• Ferritin >100 mcg/L with transferrin saturation <16% indicates anemia of chronic disease (ACD) 2
• Ferritin 30-100 mcg/L suggests combined iron deficiency and ACD 2
• Soluble transferrin receptor (sTfR) is elevated in true iron deficiency but normal/low in ACD, making it useful when available 2, 4, 5

Key Pitfalls to Avoid

• Never rely on transferrin/TIBC alone—always interpret in conjunction with serum ferritin, transferrin saturation, and clinical context including inflammatory markers 1
• Timing matters: Serum iron has significant diurnal variation (rises in morning, falls at night) and increases after meals, affecting calculated transferrin saturation 1
• In haemochromatosis monitoring: Transferrin saturation may remain elevated (>50%) even when ferritin is within target range (<50 mcg/L), and this persistent elevation may relate to ongoing symptoms 2
• Do not measure ferritin for haemochromatosis detection in actively drinking alcoholics—wait until abstinence, as ferritin decreases rapidly during abstinence 3

Practical Next Steps

• Obtain serum iron and calculate transferrin saturation as the most critical next test 1
• Check CRP or ESR to assess for inflammation that would affect ferritin interpretation 2, 1
• If transferrin saturation <20% and ferritin <30 ng/mL (or <100 ng/mL with inflammation): diagnose iron deficiency and investigate the underlying cause 1
• If transferrin saturation is normal (>20%) and ferritin is normal: iron deficiency is unlikely, and the normal transferrin level of 236 mg/dL requires no specific intervention 1