Final answer:
The patient's symptoms of excessive urination, thirst, and confusion with low blood pressure are indicative of diabetes mellitus, particularly since diabetes leads to high blood glucose levels that cause diuresis and subsequent dehydration. Option 1 is correct.
Step-by-step explanation:
The most likely cause of the patient's current symptoms, considering excessive urination, thirst, and a presentation of confusion with low blood pressure, appears to be diabetes mellitus. Diabetes mellitus causes high levels of glucose in the blood, which leads to excessive urination as the kidneys attempt to expel the excess glucose, and in turn, stimulates thirst due to loss of water.
Furthermore, if this condition advances without proper management, it can develop complications such as diabetic nephropathy, which can manifest as a variety of symptoms including frequent urination, severe tiredness, and confusion due to the impact on kidney function.