Why would a blood test give a diagnosis of lethargy?

A blood test can help diagnose lethargy by identifying underlying medical conditions that may cause fatigue or low energy levels. For instance, it can reveal anemia, thyroid dysfunction, vitamin deficiencies, or infections. Additionally, abnormal levels of electrolytes or markers of inflammation can also provide insights into the cause of lethargy. Ultimately, the results guide healthcare providers in determining the appropriate treatment or further investigations needed.