Hello! You haven t provided enough information for an accurate opinion( age,gender,other medical conditions,how long have you had these complains?). There are many possible causes for such symptoms (sleepiness,weakness). If I were your treating doctor I would first try to rule out the most common causes including: -Anemia (low red blood cells and low hemoglobin).You should run a complete blood test to confirm this. -Diabetes (high blood sugar).Run a blood sugar test to confirm this. -Hypothyroidism (underactive thyroid gland).You should get tested thyroid function :FT3 , FT4, TSH. -Low blood pressure. Once excluded these possibility I would think other options. I suggest to consult a physician and get examined. Hope my answer has helped. Take care. Dr.Rovena Murati