Constipation and Diarrhea From Diabetes

Medically Reviewed by Dany Paul Baby, MD on February 15, 2023
4 min read

Diabetes may set you up for digestive system problems like constipation, but there are many things you can do to get relief.

While everyone is different, some signs that you are constipated are:

  • You poop fewer than three times a week.
  • Your bowel movements are hard, dry, or lumpy.
  • You have to strain to go.
  • You feel bloated.
  • Your stomach hurts.

Anyone can get constipated. But when you have diabetes, changes to your body can make constipation more likely.

Digestion begins the minute you take a bite of food and ends a day or two later with a trip to the bathroom. The whole process is handled by the same part of your nervous system that controls other body functions that happen automatically, like your heartbeat and breathing.

But over time, high blood sugar can damage the tiny blood vessels and nerves in your body, including your digestive system. A speed-up or slow-down of the process in your intestines could result in diarrhea or constipation. Diabetes medications, certain foods, and related illnesses can cause diarrhea, too.

About 60% to 70% of people with diabetes have some form of nerve damage, or diabetic neuropathy. It can develop at any time, but the longer you have diabetes, the more likely it is.

When diabetes damages the nerves going to your stomach and intestines, they may not be able to move food through normally. This causes constipation, but you can also get alternating bouts of constipation and diarrhea, especially at night.

Misfiring nerves may not squeeze the muscles that mix and move the stuff in your intestines, so everything slows down. Your colon absorbs more moisture from the waste, which makes your poop harder -- and harder to pass. Constipation that lasts a long time can cause other health problems, such as fecal impaction, a hard lump of stool that blocks your rectum so nothing can get out.

Fluid that lingers in your small intestine too long can allow too much bacteria to grow. This could lead to bloating, belly pain, and diarrhea.

Nerve damage in your large intestine may let fluids move through too fast or cause problems with absorbing and releasing fluid. If that's the case, your poop could be more watery, and you'll need to go more often and urgently.

Metformin is in medicines many people take for type 2 diabetes. It helps lower your blood glucose and makes your body more sensitive to insulin. But it can also cause nausea and diarrhea when you first start taking it or when you raise the dose. Those side effects usually go away in a few weeks.

Diarrhea is a possible side effect of other diabetes drugs, too, including:

  • Acarbose (Precose)
  • Colesevelam (Welchol), and it can also cause constipation
  • Linagliptin (Tradjenta)
  • Miglitol (Glyset)
  • Saxagliptin (Onglyza)
  • Sitagliptin (Januvia)

Eating a lot of sugar-free sweeteners like maltitol, mannitol, sorbitol, and xylitol -- can cause diarrhea. They're from a family of compounds called sugar alcohols. Because your body doesn't break them down and absorb them completely, they pull extra water into your intestines.

If you have type 1 diabetes, you are at higher risk for having celiac disease. People with this disorder can't eat gluten (a protein found in grains like wheat, rye, and barley) because it damages the small intestine.

Poor diet. Many people get diabetes because they don't eat enough of the right kind of food. A poor diet can also make you constipated. Your body needs lots of insoluble fiber to have regular bowel movements. You get this kind of fiber from whole grains, fruits, and vegetables. If you cut down on carbs to help lower your blood sugar, you may also be cutting out important fiber sources.

Dehydration. Diabetes makes your kidneys work overtime trying to flush out the extra sugar from your bloodstream. You have to pee more often, which can leave you dehydrated. That makes your bowel movement harder than it should be, and your body has trouble getting it through your system.

Your first goal should be to get your blood sugar under control. That can slow down or stop more nerve damage in your intestines. As it turns out, many of the healthy choices that doctors recommend to manage diabetes will also ease constipation:

  • Eat food that's high in fiber, like whole grains, fruits, and vegetables.
  • Get regular exercise.
  • Drink plenty of water.

Fiber supplements can help deliver what you don't get from your diet alone. They make your bowel movements larger and softer so they're easier to pass. Laxatives, either over-the-counter or prescription, are another option. They either pull water into your intestines, to soften your bowel movements, or force your intestines to contract and move them along.

Talk to your doctor about unpleasant changes in your digestion. They can help you figure out what's going on and how to treat it.

You may be able to manage diarrhea and constipation by having smaller meals more often, eating fiber-rich foods, or taking medicine. Keeping your blood sugar at your target level may help lessen symptoms and stop nerve damage from getting worse.