Dr Aidin Rawshani

Diarrhea and constipation in people with diabetes


Nerve damage in the gastrointestinal tract causes diarrhea and constipation in diabetes

The fact that diabetes can cause a heart attack, stroke and other cardiovascular diseases is known to most people. However, there are not as many people who know that diabetes can affect the functioning of the gastrointestinal tract. The gastrointestinal tract contains nerves and these nerves are needed to control the functioning of the gastrointestinal tract. The intestine receives signals from the brain and is also affected by hormones in the body. Some signals lead to the fact that the stomach and intestines begin to work, while other signals urge the stomach and intestines to rest.

We cannot influence these nerves with our will, but they are automatically controlled. This type of nerves, i.e. nerves that are beyond our control, is called autonomic nerves. As described earlier in the chapter on neuropathy (nerve damage), autonomic nerves can be damaged by diabetes and this is one of the causes of problems with constipation and diarrhea in diabetes.

In addition to nerve damage, diabetes can lead to atherosclerosis (varicose veins) in the blood vessels of the gastrointestinal tract and this worsens blood flow to the stomach and intestines. That is, disorders in the functioning of the gastrointestinal tract are a complication of diabetes.

Of course, people with diabetes, as well as other individuals, may suffer from other causes of diarrhea and constipation. Several medicines given in diabetes have diarrhea and constipation as side effects.

Nerve damage (neuropathy) of the gastrointestinal tract

Approximately 50% of all people with diabetes have some kind of neuropathy (nerve damage). This has been discussed in detail in the chapter on neuropathies. Neuropathy can occur at any time during the course of the disease; the longer you have diabetes and the higher the blood sugar you have, the higher the risk of neuropathy.

If neuropathy affects the nerves of the stomach and intestines, the functioning of these organs is affected. Then the food can not be processed normally. The stomach and intestines become more difficult to contract (which is required for digestion) and absorption of nutrients becomes more difficult. This usually causes constipation, but occasionally you also get diarrhea, especially at night.


The constipation is due to the fact that the colon’s ability to contract and push food forward becomes worse in neuropathy. The passage through the colon is thus slower and this leads to more fluid being absorbed into the colon. When the liquid is absorbed, the stool becomes hard and you become constipated.


The small intestine can also become worse at pushing food forward. This means that the food stays longer than normal in the small intestine, which can lead to an increase in the number of bacteria (which we normally have in the small intestine). This can lead to diarrhea. In addition, nerve damage in the colon can also lead to food passing too fast in the colon, so that the liquid does not have time to absorb and then you get diarrhea.

Diarrhea caused by neuropathy occurs most often during the night. Diarrhea does not hurt. Some individuals may have incontinence. It is common for diarrhea to be attacked and in between, you can have normal stools or constipation.

Drugs that cause diarrhea or constipation

Metformin is probably the most commonly used drug in diabetes. Metformin lowers blood sugar and increases the sensitivity of the body to insulin. Unfortunately, metformin can lead to nausea and diarrhea at the beginning of treatment. Metformin can also cause nausea and diarrhea when increasing the dose. However, these side effects usually disappear after a few days or weeks.

Other medicines that can cause diarrhea are as follows:

  • Januvia (sitagliptin)
  • Onglyza (Saxagliptin)
  • Glyset (Miglitol)
  • Trajenta (Linagliptin)
  • Akarbos

Type 1 diabetes and gluten intolerance (celiac disease)

People with type 1 diabetes are more likely to suffer from gluten intolerance (celiac disease). If you have gluten intolerance, you can’t eat gluten, which is a protein found in wheat, rye and barley. Gluten causes an inflammatory reaction in the intestine and this leads to diarrhea.

Other causes of diarrhea and constipation in diabetes

You can also get loose stools of sweeteners such as maltitol, mannitol, sorbitol and xylitol. These sweeteners belong to the chemical group of sugar alcohols. Our gastrointestinal tract cannot break down sugar alcohols, which makes them move on to the colon where they draw water to the intestine, leading to loose stools.

Note that people with diabetes may have constipation and diarrhea for the same reasons as people without diabetes. This includes infections, inflammatory bowel diseases (Crohn’s disease, IBD), tumors, etc.

How is diarrhea caused by neuropathy treated?

First of all, it must be established that the diarrhea is due to neuropathy. This requires an investigation that excludes other (and potentially treatable) causes of diarrhea.

To treat diarrhea, there are among other options:

  • Good blood sugar control is always the first step in the treatment of diabetic complications.
  • Loperamide (Imodium) is a tablet that reduces diarrhea.
  • Food that is rich in fiber can reduce diarrhea.
  • A bulk drug may reduce diarrhea symptoms.
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