Hi. Thanks for your query. Noted the history about a 55 year old female patient and understood the concerns. Diarrhea for a week, causing weakness indicate the following: Electrolyte imbalance due to loss in the excessive diarrhea. Infection causing septicemia is a possibility. This can be diagnosed by the following ways: Get the stool and blood tested. Clinical evaluation by your Doctor. This will give an appropriate diagnosis and management. You may need the following: First of all get the electrolyte solution to ward off the weakness, plenty of fluids and semisolid foods with curds, bananas, probiotics, multivitamins and activated charcoal. A course of an antibiotic, metronidazole, Omeprazole should help you the most hence should consult a Doctor to get a prescription based medications.