Thick saliva or mucus as well as drinking excessive fluids in response to thirst can be signs of dehydration due to any cause. Excessive thirst can also be a sign of poorly controlled diabetes. Keep a record of your symptoms and when they occur. If you are concerned about your symptoms, seek the advice of a doctor.
While the list below can be considered as a guide to educate yourself about these conditions, this is not a substitute for a diagnosis from a health care provider. There are many other medical conditions that also can be associated with your symptoms and signs. Here are a number of those from MedicineNet:
Dehydration is the excessive loss of body water. There are a number of causes of dehydration including heat exposure, prolonged vigorous exercise, and some diseases of the gastrointestinal tract. Symptoms of dehydration include headache, lightheadedness, constipation, and bad breath. Treatment for dehydration is to replace lost fluids and electrolytes.
Type 2 Diabetes
Type 2 diabetes is a chronic condition that may be reversible with diet and lifestyle changes. Symptoms include excessive thirst, frequent urination, weight loss, fatigue, and an unusual odor to your urine. Most people don't know they have type 2 diabetes until they have a routine blood test. Treatment options include medications, a type 2 diabetes diet, and other lifestyle changes.
Type 1 Diabetes
Type 1 diabetes mellitus (juvenile) is an auto-immune disease with no known cause at this time, although there are a few risk factors. Symptoms of type 1 diabetes include frequent urination, unintentional weight loss, dry and itchy skin, vision problems, wounds that heal slowly, and excessive thirst. Type 1 diabetes is diagnosed with blood tests. A healthy lifestyle and controlling blood glucose levels can improve life expectancy.
Cystic fibrosis is a disease of the mucus and sweat glands. Cystic fibrosis is an inherited disease. The outcome of the disease leaves the body malnourished, with bulky and fouls smelling stools, vitamin insufficiency, gas, painful or swollen abdomen, infertility, susceptible to heat emergencies, and respiratory failure. There is no cure for cystic fibrosis, treatment of symptoms is used to manage the disease.