what causes excessive thirst
1 diabetes: Excessive thirst can be caused by high blood sugar (hyperglycemia), and is often one of the first noticeable symptoms of diabetes. 2  diabetes insipidus: With this form of diabetes, your kidneys are unable to conserve water, leading to excessive thirst.auses of Excessive Thirst. It is normal to feel thirsty after eating salty or spicy foods, or after engaging in strenuous exercise or sporting events, especially when it is hot. You may also feel thirsty when you suffer from diarrhea, vomiting, burns, or a significant loss of blood.