Excessive thirst can be caused for a variety of reasons, including having diabetes, recently consuming a salty or spicy meal or taking certain medications, according to the National Institutes of Health. Being thirsty all of the time can also be caused by a loss of bodily fluids from an extensive workout or loss of bodily fluids from infections in the body.
It's important to contact a medical professional if the excessive thirst has been going on for a while and is unexplained. It's also important to keep an eye on other possible symptoms, including blurry vision and fatigue, as well as urinating more than 5 quarts per day, according to the National Institutes on Health. A doctor may administer certain tests to determine the cause of excessive thirst, including a blood glucose level test and a serum calcium test.