Is Transferrin useful for fatigue?

Transferrin is a protein that transports iron in the blood. Low transferrin levels or low transferrin saturation can indicate iron deficiency, which is a known cause of fatigue. However, transferrin alone is not a direct marker for fatigue. The evidence for its usefulness is indirect: iron deficiency anemia is a well-established cause of exhaustion, but many other factors (sleep, stress, thyroid, inflammation) contribute. A transferrin test without concurrent iron and ferritin measurement has limited interpretability. Additionally, inflammation or liver disease can alter transferrin levels. Evidence grade: unclear or practice (routine clinical use). Caveat: Not a standalone fatigue diagnostic; persistent fatigue warrants medical evaluation.