Laboratory Testing for Female Patient with Fatigue
For a female patient presenting with fatigue, order a comprehensive initial panel including: β-hCG (pregnancy test), CBC, complete metabolic panel (electrolytes, glucose, BUN, creatinine, liver function), TSH with free T4, and ferritin. Add a hormonal panel (FSH, LH, estradiol, prolactin, and testosterone) if menstrual irregularities are present or if initial screening is unrevealing 1.
Initial Essential Tests
Start with these core laboratories that detect the most common and serious causes of fatigue:
- β-human chorionic gonadotropin (β-hCG) - Rule out pregnancy first 1
- Complete blood count (CBC) - Detect anemia, infection, or hematologic disorders 1
- Complete metabolic panel including:
- Electrolytes, glucose, bicarbonate
- BUN and creatinine (renal function)
- Liver panel 1
- TSH and free T4 - Thyroid dysfunction is a common endocrine cause of fatigue 1, 2
- Ferritin - Iron deficiency is particularly common in women 3
When to Add Hormonal Testing
Add the full hormonal panel if:
- Menstrual irregularities are present (amenorrhea, oligomenorrhea)
- Initial screening tests are normal but fatigue persists
- Signs of hormonal dysfunction exist (galactorrhea, hirsutism, acne, hot flashes)
The hormonal panel should include 1:
- FSH and LH - Pattern is critical; low/low-normal LH with normal FSH suggests functional hypothalamic amenorrhea
- Estradiol (E2) - Values <50 pg/mL indicate hypoestrogenism
- Prolactin - Elevated levels suggest prolactinoma or other causes of hyperprolactinemia
- Total testosterone - Only if clinical hyperandrogenism present (hirsutism, acne, male pattern alopecia)
- DHEA-S - Only with clinical hyperandrogenism 1
Additional Tests in Specific Scenarios
If chronic illness is suspected (based on history or physical exam):
- ESR and/or CRP - Elevated levels suggest chronic inflammatory conditions 1
- Hemoglobin A1C if glucose is elevated 1
If adrenal insufficiency is suspected (postural hypotension, salt craving, weight loss):
- Morning cortisol and ACTH
- Consider cosyntropin stimulation test 4
Critical Timing Considerations
For hormonal testing to be interpretable, blood must be drawn:
- Early morning hours (between 7-9 AM for cortisol, testosterone)
- Days 1-5 of menstrual cycle for FSH, LH, estradiol 5
- Fasting state for some hormones 5
Improper timing renders results uninterpretable and wastes resources 6.
Important Caveats
The pattern of hormone levels matters more than absolute values 1. For example, in functional hypothalamic amenorrhea, you'll see characteristically low/low-normal LH with normal FSH (FSH usually higher than LH), and E2 <50 pg/mL.
Avoid over-testing initially. Research shows that pathology testing in tired patients has a low pickup rate for serious disease 3. The tests listed above capture the most clinically significant causes while avoiding unnecessary expense.
Do not routinely order: AMH, 17-hydroxyprogesterone (unless late-onset CAH suspected with hyperandrogenism), or DHEA unless specific clinical indicators are present 1.
What Not to Do
- Don't order a "shotgun" hormonal panel on every fatigued woman - reserve it for those with menstrual dysfunction or unrevealing initial workup
- Don't order sex hormones without proper cycle timing - you'll get uninterpretable results 6, 5
- Don't skip the pregnancy test - it's the most important first test in any reproductive-age woman 1