One of the most common causes of dry mouth and frequent urination is diabetes. Diuretics, such as caffeine and alcohol, which dehydrate the body and flush fluids out of the system, are another frequent cause. Frequent urination can also indirectly be a cause of dry mouth, as many medications prescribed for overactive bladders cause dry mouth.
Type 1 and type 2 diabetes cause both of these symptoms. In fact, those symptoms are often the earliest and most noticeable signs of diabetes. The frequent urination is a result of low levels of insulin that are unable to properly break down glucose in the bloodstream. Normally, insulin levels break down glucose and convert it into energy. When levels are too low to sufficiently accomplish that task, the bloodstream is flooded with glucose, which causes more water and fluid to enter the bloodstream. As a result, more fluids are flushed through the kidneys, causing diabetics to urinate more frequently. Another side effect of this process is thirst and dry mouth. People who chronically experience these symptoms should consult a medical professional.
Diuretics cause the body to flush water and fluids out of the system by urination. This naturally leads to dry mouth and frequent urination. People suffering from these symptoms who don't have diabetes should assess their caffeine and alcohol intake, as both are diuretics that dehydrate the body. There are also diuretics in the food realm, such as cranberries, which can increase urination and cause dry mouth. Water pills, which are often taken to lose weight, also cause the body to flush out water. Alleviating the symptoms may be as simple as removing diuretic substances from one's diet.
Interestingly enough, medications that treat overactive bladders — bladders that send signals to the brain that prompt urination even when the bladder isn't full — cause dry mouths in many individuals. In this case, dry mouth and frequent urination do not occur at the same time. Instead, dry mouth is a side effect of efforts to cure frequent urination. Fortunately, dry mouth caused by medications can be alleviated. Surprisingly, drinking more water won't necessarily cure the problem, but there are over-the-counter medications that may help. Chewing a stick of sugar-free gum can be another very effective way of increasing saliva flow in the mouth. Sugar-free candy can also help in the same way.