The most common cause of thirst with frequent urination is diabetes, and these symptoms are typically found in both type 1 and type 2. Other conditions that sometimes lead to this symptom are liver disease, pregnancy, and some kidney disorders. They can also be caused by certain types of medication and lifestyle. Research seems to show that most conditions that lead to excess urination generally result in thirst, and conversely, drinking a lot of liquid leads to frequent urination.
People with diabetes often experience severe thirst with frequent urination. One function of the kidneys is to metabolize sugar so the body can use it as energy. Those suffering from diabetes produce more sugar than their kidneys can process. The sugar that has not been metabolized is instead deposited in the urinary tract, creating excess urine. Frequent urination typically leads to thirst, which only adds to the need to urinate.
Kidney disorders that lead to these symptoms are generally related to the kidneys' inability to metabolize nutrients. Just as in the case of diabetes, these nutrients are turned into urine, which results in more frequent urination and thirst. Some kidney disorders that could lead to this condition are atherosclerosis, urinary tract infection, and kidney infection.
Thirst with frequent urination can also be caused by a disorder called Falconi’s syndrome, a condition involving the malfunction of the tubes that lead to the kidneys. In this condition, excess salts, sugars, and potassium are produced and deposited directly into the urine, causing frequent urination. The cause of this disease is unclear, but it is believed to be genetic and typically becomes symptomatic in infancy.
In some cases, these symptoms are caused by normal conditions, such as pregnancy, overexertion, or heat exposure. Overexertion in exercise or work can sometimes cause thirst. In addition, becoming too hot or too cold can sometimes trigger the need to consume liquids. This is considered normal and is generally no cause for alarm. Women who are pregnant generally urinate frequently, because of added pressure on the urinary tract.
Dehydration occurs when fluid leaves the body but is not replaced. Human bodies are thought to be about 75% water, so the need to keep hydrated is critical to normal body function. Dehydration causes extreme thirst because the body needs to replace the fluids it has lost. This thirst naturally leads to excessive urination. Only when the fluid coming in exceeds the fluid going out will this condition stabilize.