To identify the potential health problem causing your fatigue based on the suggested lab tests (CBC, TSH, CMP), we can follow a systematic approach:

  1. Complete Blood Count (CBC) – Rule Out Anemia Fatigue is a classic symptom of anemia. Key CBC findings:

Low Hemoglobin (Hb) & Hematocrit (Hct) → Confirms anemia.
Microcytic anemia (low MCV):
Iron deficiency (check ferritin, TIBC, serum iron)
Chronic disease anemia (elevated ferritin)
Macrocytic anemia (high MCV):
Vitamin B12 or folate deficiency (check B12, folate levels)
Normocytic anemia (normal MCV):
Chronic kidney disease (CKD) → Check creatinine (CMP)
Hemolysis or bone marrow disorder → Check reticulocyte count

  1. Thyroid-Stimulating Hormone (TSH) – Rule Out Thyroid Dysfunction High TSH + Low Free T4 → Hypothyroidism (common cause of fatigue) Low TSH + High Free T4 → Hyperthyroidism (can also cause fatigue) Normal TSH → Thyroid likely not the cause
  2. Comprehensive Metabolic Panel (CMP) – Check Electrolytes, Kidney, Liver, Glucose Electrolyte imbalances: Low sodium (hyponatremia) → Could indicate adrenal insufficiency (check cortisol) Low potassium (hypokalemia) → Could suggest aldosterone issues High calcium (hypercalcemia) → Could indicate hyperparathyroidism Kidney function: High creatinine/BUN → Possible CKD (fatigue due to uremia) Liver function: Elevated AST/ALT → Liver disease (fatigue is common) Glucose abnormalities: High glucose → Diabetes (fatigue due to poor glucose control) Low glucose → Hypoglycemia (can cause fatigue) Next Steps if Initial Tests Are Normal If CBC, TSH, and CMP are normal, consider:

Vitamin D deficiency (check 25-OH Vitamin D)
Sleep disorders (sleep apnea, insomnia)
Chronic fatigue syndrome (diagnosis of exclusion)
Depression or anxiety (mental health screening)
Adrenal insufficiency (check morning cortisol & ACTH)
Chronic infections (EBV, Lyme disease, HIV)
Summary of Likely Causes Based on Initial Tests
Test Possible Issue Next Steps
CBC (Low Hb) Anemia (iron/B12/folate deficiency, CKD) Check ferritin, B12, folate, reticulocyte count
TSH (High) Hypothyroidism Check Free T4, thyroid antibodies
CMP (Abnormal electrolytes/kidney) Electrolyte imbalance, CKD, liver disease Further workup based on specific abnormality
Would you like help interpreting your specific lab results? If you enter them as parameters for AI-driven SmrtX Diagnosis API, it can give a more precise analysis.