Constipation with frequent urination are not always directly connected, and each has a wide range of causes. An individual may suffer from overactive bladder syndrome, which causes the bladder to contract resulting in the frequent need to urinate, while at the same time, suffer from constipation due to consuming large amounts of dairy products. In other cases, these symptoms may be the result of one underlying condition, such as pregnancy, voiding dysfunction, or hypokalemia, which is a low amount of potassium in the blood.
In many cases, constipation and frequent urination are not symptoms of one condition, but may be caused by different factors. There are hundreds of factors that can cause a person to become constipated but some of the most common include infrequent exercise, lack of fiber in the diet, stress, irritable bowel syndrome, laxative abuse, dehydration, and disorders of the colon or rectum. Similarly, there are a number of possible causes of frequent urination, including overactive bladder syndrome and the use of diuretics, which are medications that treat high blood pressure and diabetes. When these factors occur at the same time, there is a high likelihood of experiencing both constipation and frequent urination, although the causes may be unrelated.
It is also possible for these symptoms to be caused by a single underlying factor. Pregnancy is one condition that can cause both constipation and frequent urination. Frequent urination is common during pregnancy because the body contains more fluid during this time, the baby can put pressure on the bladder, and hormones produced during pregnancy cause the body to urinate more often. At the same time, the increase in hormones during pregnancy also causes the muscles in the intestines to become sluggish, slowing down the movement of food and allowing the intestines to absorb all of the water in the food. By the time the end products make it to the rectum, they are often less bulky and fail to stimulate the rectum to perform its job of sending a message to the brain that it is time for a bowel movement. The result is constipation.
Another underlying cause of constipation with frequent urination occurs in children who have voiding dysfunction. Voiding dysfunction occurs when children lack normal function in the muscles that control urination, which are known as sphincter and bladder muscles. These children urinate frequently because their bladder holds far less urine than normal, and the muscles contract automatically. These muscles also control bowel movements, and when they do not function appropriately, this can also cause constipation.
When potassium levels in the blood are too low, it's known as hypokalemia. Potassium plays an integral role in muscle function and the regulation of fluids in the body. For these reasons, the lack of potassium can cause both constipation and frequent urination.