From the Guidelines
For generalized body weakness, a comprehensive laboratory workup should include a complete blood count (CBC), thyroid-stimulating hormone (TSH), B12, calcium, electrolytes, creatinine, alanine transaminase (ALT), lipid panel, and hemoglobin A1c (HbA1c) as recommended by the most recent guidelines 1. These tests help identify common causes of weakness such as anemia, electrolyte imbalances, thyroid disorders, nutritional deficiencies, and diabetes.
Key Laboratory Tests
- Complete blood count (CBC) to check for anemia or other blood disorders
- Thyroid-stimulating hormone (TSH) to assess thyroid function
- Vitamin B12 levels to check for deficiency
- Electrolyte panel to evaluate electrolyte imbalances
- Creatinine and alanine transaminase (ALT) to assess kidney and liver function
- Lipid panel to check for dyslipidemia
- Hemoglobin A1c (HbA1c) to check for diabetes Additional tests may be necessary based on the patient's symptoms, medical history, and physical examination findings.
Considerations for Testing
The choice of laboratory tests should be guided by the patient's clinical presentation and medical history, as generalized weakness can stem from numerous conditions affecting various body systems, including neurological, muscular, endocrine, cardiovascular, and psychological factors 1. Early diagnosis through appropriate testing allows for targeted treatment of the underlying cause, which can significantly improve morbidity, mortality, and quality of life. It is essential to prioritize the most recent and highest-quality guidelines when making decisions about laboratory testing for generalized body weakness, as recommended by the 2025 guidelines 1.
From the Research
Lab Tests for Generalized Body Weakness (Asthenia)
The following lab tests are indicated for generalized body weakness, also known as asthenia:
- Full blood count (FBC) to check for anemia, which can cause weakness, lethargy, and shortness of breath 2
- Iron studies, including serum iron, ferritin, and transferrin saturation, to diagnose iron deficiency anemia 2, 3, 4
- Vitamin B12 and folate levels to diagnose deficiencies, which can cause macrocytic anemia 2, 5
- Reticulocyte count to evaluate the bone marrow's response to anemia 4, 5
- Reticulocyte hemoglobin content (CHr) to diagnose iron deficiency and iron deficiency anemia, and to monitor iron therapy 4
- Mean corpuscular volume (MCV) to classify anemia and guide differential diagnosis 3, 5
- Red blood cell distribution width index (RDW) to evaluate anisocytosis and diagnose iron deficiency anemia 5
- Peripheral blood smear to evaluate red blood cell morphology 6
- Lactate dehydrogenase, haptoglobin, and bilirubin levels to evaluate hemolysis and diagnose hemolytic anemia 6
Diagnostic Approach
The diagnostic approach to generalized body weakness involves:
- A thorough history and physical examination to identify potential causes of anemia 6
- A complete blood cell count (CBC) to evaluate red blood cell indices and classify anemia 2, 3, 6
- Supplemental tests, such as iron studies, vitamin B12 and folate levels, and reticulocyte count, to diagnose specific causes of anemia 2, 3, 4, 5, 6