Final answer:
In diabetes mellitus, the pH level of the blood is decreased due to a condition called diabetic ketoacidosis. This disrupts biological processes and leads to symptoms such as frequent urination and excessive thirst.
Step-by-step explanation:
In diabetes mellitus, the pH level of the blood is decreased due to a condition called diabetic ketoacidosis. This occurs when the body breaks down fats for energy, leading to the production of ketone bodies that increase the acidity of the blood. The lower pH disrupts biological processes in the body. The symptoms of diabetic ketoacidosis include frequent urination, excessive thirst, and dehydration.