Initial Blood Work for a 20-Year-Old Female with Fatigue and Malaise
For a young woman presenting with nonspecific fatigue and feeling unwell, initial blood work should include a complete blood count (CBC) with differential, comprehensive metabolic panel, thyroid function tests (TSH, free T4), iron studies (serum iron, ferritin, transferrin saturation), inflammatory markers (CRP, ESR), and vitamin D levels. 1
Core Laboratory Assessment
Hematologic Evaluation
- Complete blood count (CBC) with differential to assess for anemia, which is a common reversible cause of fatigue in young women 1
- Mean corpuscular volume (MCV) to evaluate red blood cell size and guide further workup 1
Iron Status Assessment
Iron deficiency is particularly common in menstruating women and represents a highly treatable cause of fatigue:
- Serum ferritin - the primary screening test for iron stores 1
- Serum iron and transferrin saturation - provides additional information when ferritin is equivocal 1
- Transferrin levels - completes the iron panel assessment 1
Low iron stores and low hemoglobin are examples of reversible causes of persistent fatigue that should be actively identified 1
Metabolic and Endocrine Screening
- Comprehensive metabolic panel including glucose, electrolytes, kidney function (creatinine), and liver function tests (ALT, AST) 1
- Thyroid function tests (TSH and free T4) - thyroid disorders commonly present with fatigue and weight changes in young women 1
Inflammatory Markers
- C-reactive protein (CRP) - elevated inflammatory markers can indicate underlying inflammatory conditions 1
- Erythrocyte sedimentation rate (ESR) may be considered as an additional inflammatory marker 1
Nutritional Assessment
- Vitamin D (25-OH vitamin D) - deficiency is linked to muscle fatigue and correlates with self-reported fatigue 1
- Vitamin B12 and folate - particularly if MCV is elevated or if there are neurologic symptoms 1
- Magnesium - low levels have been linked to muscle fatigue 1
Important Clinical Considerations
Age and Gender-Specific Factors
Fatigue appears most marked in female patients and those less than 60 years old, making thorough evaluation particularly important in this demographic 1
Red Flags Requiring Expanded Workup
If the patient presents with additional concerning features, expand the initial panel:
- Headaches with visual symptoms or nausea - consider hypophysitis or other endocrine disorders 1
- Weight loss - add liver function tests if not already included 1
- Muscle weakness - consider creatine kinase and additional neurologic evaluation 1
- Joint pain or rash - add autoimmune markers including ANA 1
Timing of Follow-Up Testing
- Repeat basic blood tests after 8-10 weeks if iron supplementation is initiated, not earlier, as ferritin levels may be falsely elevated immediately after iron infusion 1
- If initial workup is normal but symptoms persist beyond one month, consider reassessment as fatigue lasting more than a month warrants thorough investigation 1
Common Pitfalls to Avoid
Do not attribute persistent fatigue to stress or depression without completing objective laboratory assessment, as multiple reversible physiologic causes must be excluded first 1
Do not rely 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 1
Do not overlook the multifactorial nature of fatigue - physical assessment combined with biochemical and hematological testing provides the most complete picture 1