• Constipation can cause nausea, as a buildup of stool in your intestines can allow food to linger in your stomach and lead to feelings of nausea or bloating. 
  • A buildup of stool can also result in an imbalance in your gut bacteria, which may cause nausea.
  • This article was medically reviewed by Rudolph Bedford, MD, a gastroenterologist at Providence Saint John’s Health Center in Santa Monica, California.
  • Visit Insider’s Health Reference library for more advice.

Constipation is a common digestive problem that involves the inability to pass stool. Occasionally, constipation is accompanied by feelings of nausea, and the urge to vomit. If you’ve ever wondered why you might feel nauseous while constipated, here is how it happens. 

Why constipation can make you nauseous

The main symptom of constipation is the inability to evacuate stool more than three times a week. It can also involve straining while passing stool, having lumpy or hard stool, or needing to use your fingers to remove stool from your anus.  

“In general, it’s recommended to empty your bowels at least once every two to three days. Once you’ve gone four days or more without having a bowel movement, something has gone wrong. It’s at this time you can expect unpleasant symptoms like nausea to occur,” says Bryan Curtin, M.D., MHSc, a gastroenterologist at Mercy Medical Center in Baltimore, Maryland.

This is because constipation happens when your large intestine has absorbed too much water from your stool, making the stool hard and difficult to push out of the body. This buildup of stool can block food in the stomach from traveling to the intestines, which leaves food to linger in the stomach and cause bloating and nausea. 

The excess waste in your colon can also lead to an imbalance in your gut bacteria. “The small intestine contains a lot of bacteria because that’s where most of your food absorption happens,” But when you are constipated, that bacteria overgrows and produces methane. 

Methane-producing gut bacteria has been associated with slowing of the gut and constipation in previously done studies. The build-up of methane also creates feelings of nausea. 

Other causes of nausea 

Of course, nausea doesn’t only occur when you are constipated. Other causes of nausea include:

Food poisoning 

While food poisoning symptoms vary from person to person, one of the most common is nausea. The time it takes for the symptoms of food poisoning to show up depends on the type of food poisoning you have. Symptoms could show up as soon as 30 minutes to a week after you’ve consumed the contaminated food. Food poisoning could be a culprit if you’ve consumed foods like undercooked meat and poultry, contaminated fruits and vegetables or raw seafood.  

Food intolerance

If you suffer from persistent nausea, your diet might be responsible. Consuming a diet that’s too low in fiber and fluids can cause constipation and induce nausea. On this, Curtin says, “People sometimes experience nausea as a result of consuming processed foods in excess. Lactose, fructose and processed sugars are most likely to cause food intolerance-related nausea.” 

He further explains that,  “Food intolerance is when your body isn’t able to handle large amounts of certain types of food. The most common type is lactose intolerance. When people with lactose intolerance consume large amounts of lactose, they get bloating, diarrhea and nausea.”

Acid reflux 

Acid reflux is a very common digestive disorder worldwide. While the most prevalent symptom of acid reflux is heartburn (a burning sensation that starts in the chest and radiates towards the mouth), nausea is also a popular symptom. 

Digestive issues 

Digestive issues such as Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) are also common causes of both nausea and constipation. People who suffer from these issues report that nausea is one of the first symptoms they experience. A UCLA study reported that around 4 out of 10 women and nearly 3 out of 10 men with IBS report nausea.

Medication 

Sometimes the inactive ingredients in medications could make a person feel nauseated. Taking certain medication like antidepressants, strong painkillers, and some allergy medication may also be a culprit. 

Pregnancy 

In the first trimester, many women may experience morning sickness, which includes nausea and vomiting. Even though it’s called morning sickness, it can occur at any time of the day. It is often one of the first signs of pregnancy.  

Stress 

When you are stressed some stress hormones released by your body can upset your digestive system. This can affect the way food moves through your body, causing you to experience nausea and stomach cramps. 

How to treat nausea  

If your nausea is brought on by constipation, you should try to treat the constipation itself first. According to Hastin taking a laxative or a stool softener may help ease your nausea. 

You can also take over-the-counter treatments like Pepto Bismol or Gaviscon.

If you don’t have immediate access to over-the-counter medication here are a couple of tips to get temporary relief from nausea, no matter what the cause may be:

  • Place a heating pad against your stomach. This can help relax the stomach muscles and ease your nausea. 
  • Sit up straight to avoid crunching your stomach, especially after eating. 
  • Apply a cool compress to the back of your neck.
  • Drink some ginger tea. Many studies show that ginger is an effective and inexpensive treatment for nausea. 

“However, if you have persistent nausea, that’s occurring over the course of a week or a month, then you should see a doctor,” advises Curtin.

For more information, read about these 6 home remedies for nausea, and the best nausea medications

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