Evaluation of Fatigue in Young Women

Initial Laboratory Assessment

The American Gastroenterological Association recommends a complete blood count (CBC) with differential to assess for anemia, a common reversible cause of fatigue in young women 1, 2, 5
The European Society of Cardiology suggests measuring mean corpuscular volume (MCV) to evaluate red blood cell size and guide further workup 4
Initial blood work should include iron studies, such as serum ferritin, serum iron, and transferrin saturation, to identify iron deficiency, a highly treatable cause of fatigue 1, 2, 3, 4
A comprehensive metabolic panel, including glucose, electrolytes, kidney function, and liver function tests, is recommended to assess for underlying metabolic disorders 4, 6
Thyroid function tests, such as TSH and free T4, should be performed to evaluate for thyroid disorders, which commonly present with fatigue and weight changes in young women 7

The American College of Gastroenterology recommends measuring C-reactive protein (CRP) to identify underlying inflammatory conditions 1, 2, 5
Erythrocyte sedimentation rate (ESR) may be considered as an additional inflammatory marker 1
Vitamin D levels should be measured, as deficiency is linked to muscle fatigue and correlates with self-reported fatigue 1, 2, 5
Vitamin B12 and folate levels should be assessed, particularly if MCV is elevated or if there are neurologic symptoms 4

The American Heart Association notes that fatigue appears most marked in female patients and those less than 60 years old, making thorough evaluation particularly important in this demographic 1, 2, 5
Red flags, such as headaches with visual symptoms or nausea, weight loss, muscle weakness, joint pain, or rash, require expanded workup, including additional laboratory tests and clinical evaluation 7, 8

The European Society for Clinical Nutrition recommends repeating basic blood tests after 8-10 weeks if iron supplementation is initiated, as ferritin levels may be falsely elevated immediately after iron infusion 3
The American Gastroenterological Association advises against attributing persistent fatigue to stress or depression without completing objective laboratory assessment, as multiple reversible physiologic causes must be excluded first 1, 2, 5
The American College of Cardiology warns against relying on ferritin alone in the presence of inflammation, as ferritin is an acute phase reactant and may be falsely normal or elevated despite true iron deficiency when CRP is elevated 3, 4