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What is the main cause of constipation?

Constipation is a very common gastrointestinal disorder that affects people of all ages. It is characterized by infrequent, difficult, or incomplete bowel movements. There are many potential causes of constipation, but the most common causes include:


Diet plays a major role in causing or relieving constipation. Some dietary factors that can lead to constipation include:

  • Low fiber intake – Fiber adds bulk to stool and helps it move through the intestines more easily. Low fiber diets or inadequate fluid intake can make stools hard and difficult to pass.
  • Dairy products – Milk, cheese, and other dairy products can cause constipation in some people due to lactose intolerance.
  • Processed foods – Heavily processed foods that are low in fiber can contribute to constipation.
  • Not enough fruits and vegetables – Fruits and veggies are great sources of fiber and nutrients that can help prevent constipation.
  • Dehydration – Not drinking enough fluids can cause stools to become hard and dry, and more difficult to pass.


Many medications can cause or worsen constipation including:

  • Opioid pain medications
  • Antidepressants
  • Antacids containing aluminum or calcium
  • Anti-seizure medications
  • Blood pressure medications
  • Iron supplements

These medications can slow digestion, decrease intestinal contraction, or absorb fluid from the colon which can lead to hard, dry stools.

Lifestyle Factors

Daily habits and lifestyle choices can also contribute to constipation such as:

  • Lack of exercise – Regular physical activity helps stimulate bowel movements.
  • Stress and anxiety – Mental health issues can disrupt digestion and cause constipation.
  • Travel or changes in routine – Traveling and disruptions to daily routine can affect bowel habits.
  • Resisting bowel urges – Ignoring the urge to have a bowel movement can weaken the bowel muscle over time.
  • Older age – Constipation is more common in older adults due to slowed digestion.

Diseases and Conditions

Certain medical conditions can also lead to constipation including:

  • Irritable bowel syndrome (IBS)
  • Inflammatory bowel disease (IBD)
  • Diabetes
  • Hypothyroidism
  • Neurological disorders such as Parkinson’s disease
  • Spinal cord injuries
  • Pelvic floor dysfunction
  • Anal fissures
  • Colon cancer

These conditions can impair digestion, slow motility, or cause painful defecation leading to avoidance of bowel movements.


Bowel obstructions can mechanically block stool passage and result in constipation. Causes include:

  • Colorectal cancer
  • Hernias
  • Anal strictures
  • Foreign bodies
  • Adhesions or scar tissue
  • Fecal impactions

Severe constipation with vomiting, abdominal pain and swelling may indicate a bowel obstruction, which requires urgent medical care.

Specific Populations at Risk

While anyone can develop constipation, some groups at higher risk include:

Infants and Children

Constipation is very common in infants as their digestive systems mature. Introducing solids, dietary changes, withholding stools, stress or changes in routine can provoke constipation in young kids.

Pregnant Women

Hormonal changes, pressure from the enlarging uterus, iron supplements, and increased water absorption may cause constipation during pregnancy.

Older Adults

Older adults face increased risk due to slowed digestion, medications, low fluid intake, low physical activity, and diseases affecting the colon.


Women are more prone to constipation than men, often due to hormonal fluctuations. Constipation is common during pregnancy, after childbirth, and near menstrual periods.


Constipation is diagnosed based on symptoms such as:

  • Passing fewer than 3 stools per week
  • Lumpy or hard stools
  • Straining during bowel movements
  • Feeling of incomplete emptying
  • Abdominal pain or bloating

Your doctor will perform a physical exam and take a medical history. You may need testing such as bloodwork, imaging, or colonoscopy to identify an underlying cause.


Constipation can usually be managed with lifestyle changes and over-the-counter laxatives if needed. Treatments may include:

  • Increasing fiber intake gradually
  • Drinking more fluids
  • Exercising regularly
  • Establishing regular toilet habits
  • Treating underlying conditions
  • Switching medications if possible
  • Osmotic laxatives like polyethylene glycol
  • Stimulant laxatives like senna
  • Stool softeners like docusate

For severe or chronic constipation, prescription medications or surgery may be recommended. Seek urgent care for constipation accompanied by vomiting, fever or rectal bleeding.


You can help prevent constipation by:

  • Eating a high fiber diet with fruits, vegetables, beans, nuts and whole grains
  • Drinking plenty of water and fluids
  • Getting regular exercise like walking, yoga or cycling
  • Establishing a bathroom routine and not delaying bowel urges
  • Managing stress through meditation, deep breathing or relaxation techniques
  • Consulting your doctor before starting any new medications


Constipation generally results from a combination of factors that affect digestion and bowel function. The most common causes include inadequate fiber and fluid intake, lack of exercise, medications, various medical conditions, and ignoring the natural urge to have a bowel movement. While constipation can be uncomfortable or even painful, it’s often preventable and treatable with simple lifestyle measures and over-the-counter remedies. However, severe or persistent constipation may require medical evaluation to identify and address an underlying disorder.