By John McElligott, MD

Question: I am incredibly thirsty all the time. I drink plenty of water, coffee, juice and bottled iced tea, but just can’t seem to get enough. Is something wrong with me?

There are a number of reasons for being so thirsty, but my main concern is that excessive thirst could be symptomatic of diabetes.

First, any substance in the blood in excess will require water to be eliminated, which can lead to excessive urination, leading to thirst, right? For example, excessive sugar in the blood “spills” into the urine and requires water to be excreted. Thus, patients with diabetes mellitus typically complain of excessive thirst and urination.

The blood sugar level has to get above about 180-200 mg/dl for sugar to spill into the urine. Below that level, the sugar is reabsorbed after being filtered by the kidneys. So, it’s easy to tell if a person’s excessive thirst and/or urination is caused by diabetes mellitus. The urine will show sugar, and the blood sugar level will be elevated.

Truckers are prone to diabetes because of weight gain and diet. This causes insulin resistance and then begins the thirst, increased urination, and increased eating. So it’s important to get checked out.

Other possibilities include endocrine or kidney disease or just a habit of drinking a lot of fluid. Or it could be something known as “psychogenic” water drinking, which is a psychological or emotional disorder. Some people just have a habit of drinking and drinking. It’s generally easy to diagnose if it’s physical or psychological from the medical history and, if necessary, do laboratory testing. Simply withholding water (under strict medical supervision) will show that before becoming dehydrated a patient with psychogenic water drinking will secrete a hormone called vasopressin, resulting in a concentration of urine. Laboratory testing can help determine what is happening and what the next best steps are to take with regards to treatment.

In your case, this is not very likely since this disorder would not allow you to drive very far without having to urinate. I have seen only one case in my career, and it was an impressive display of passing water every two minutes.