Constipation

Why it happens, how it is treated, and when it should be investigated.

What is constipation?

Constipation does not mean only going to the lavatory infrequently.

A person may have one or several of the following:

• Opening the bowels fewer than three times a week,
• Hard or dry stools,
• Excessive straining when opening the bowels,
• Stools that pass with difficulty,
• A feeling of not emptying completely,
• Spending a long time in the lavatory.

So not everyone who does not open their bowels every day is constipated.

Normal stool frequency varies from person to person. What also matters is that the person passes stool comfortably and feels adequately emptied afterwards.

Why does constipation happen?

Constipation has no single cause.

In some people lifestyle and diet matter; in others the movements of the large bowel are slow. In a further group the stool reaches the rectum normally but the pelvic floor and the muscles around the anus do not work properly as it is passed.

Put simply, there are three important mechanisms:

1. Normal-transit constipation The time the stool takes to move through the bowel is largely normal, but the person finds opening the bowels difficult or incomplete.

2. Slow-transit constipation The large bowel moves the stool along more slowly than normal.

3. Defecation disorder Although the stool reaches the rectum, the coordination of the pelvic floor and anal muscles is not right as it is expelled.

This distinction matters particularly in patients who do not respond to standard treatment. The 2026 AGA recommendations draw attention in particular to assessing anorectal function in suitable patients before constipation is called resistant.

Does diet cause constipation?

Yes, in some people it is an important factor.

Inadequate fibre intake, inadequate fluid intake and certain eating habits can make constipation easier.

Vegetables, fruit, pulses and whole grains are natural sources of fibre.

About 22–34 grams of fibre a day is recommended for adults, depending on age and sex. But increasing fibre suddenly can cause gas and bloating, so increasing it gradually is more suitable.

Does drinking a lot of water always cure constipation?

No.

Increasing fluid intake matters in a person who is taking too little or who is dehydrated. Enough fluid should also be taken when fibre intake is increased.

But a person who already drinks enough may not have their chronic constipation treated by drinking a great deal more water alone.

Does inactivity matter?

Regular physical activity may support bowel function.

Constipation may be more common in people who are inactive for long periods, confined to bed or elderly. Regular movement is part of both preventing and treating constipation.

Does putting off going to the lavatory cause constipation?

Yes.

Constantly putting off the urge to open the bowels may over time contribute to the stool staying longer in the bowel and hardening.

So the need to open the bowels should not be postponed where possible.

The movements of the large bowel naturally increase after breakfast and other meals in particular. This physiological reflex can be used to build a regular lavatory habit.

Which drugs can cause constipation?

A good many drugs can contribute to constipation.

For example, some:

• Strong painkillers of the opioid type,
• Iron preparations,
• Certain calcium-containing products,
• Anticholinergic drugs,
• Some antidepressants,
• Some blood pressure drugs,
• Drugs used in the treatment of Parkinson’s disease

may cause constipation or worsen existing constipation.

But a prescribed drug thought to be causing constipation should not be stopped without speaking to the doctor.

Can another condition lie behind constipation?

Yes.

Constipation may sometimes be associated with:

• An underactive thyroid,
• Diabetes,
• Coeliac disease,
• Parkinson’s disease and certain neurological conditions,
• Pelvic floor disorders,
• Structural narrowing in the bowel.

Rarely, tumours of the large bowel or rectum may also cause new constipation.

But the great majority of people with constipation do not have cancer.

Are constipation and IBS the same thing?

No.

Constipation may occur on its own.

There is also a type of irritable bowel syndrome in which constipation predominates: IBS-C (constipation-predominant IBS).

In IBS, constipation is usually accompanied by recurrent abdominal pain, and the pain may be related to opening the bowels.

Although the treatments are similar in some respects, the two conditions are not the same.

What is a pelvic floor problem?

This matters particularly in patients who have been constipated for many years.

Normal defecation requires the rectum and the muscles around the anus to work in a coordinated way. Some people cannot relax the muscles that should relax while trying to pass stool, or tighten them instead.

The patient may describe it as:

“The stool is there but I cannot get it out.”

“I cannot empty completely.”

“I have to strain for a very long time.”

In these patients, using a stronger laxative alone may not solve the problem.

How is the diagnosis made?

In most patients assessment begins with a good history and physical examination.

Stool frequency, stool consistency, straining, the feeling of incomplete emptying, medication, diet and how long the complaint has lasted are all assessed.

Where necessary, rectal examination can also give important information.

Does everyone with constipation need a colonoscopy?

No.

Having constipation does not automatically mean a colonoscopy is needed.

The decision is made according to the patient’s age, bowel cancer screening status, family history and any accompanying alarm symptoms.

More detailed assessment may be needed particularly where there is blood in the stool, unexplained weight loss, anaemia or a marked new change in bowel habit.

Are there special tests for constipation?

Yes. But they are not done for everyone.

Certain special tests may be used particularly in constipation that does not improve despite standard treatment.

Anorectal manometry

Assesses how the muscles of the rectum and around the anus work during defecation.

Balloon expulsion test

Assesses whether a small balloon placed in the rectum can be expelled by the patient’s normal defecation effort.

Colonic transit study

Investigates how fast or slowly the stool moves through the large bowel.

Defaecography

Can help assess the anatomical and functional behaviour of the rectum and pelvic floor during defecation.

In the 2026 AGA update, anorectal manometry and the balloon expulsion test have an important place in treatment-resistant constipation in particular.

How is constipation treated?

Treatment should be arranged according to the cause.

The first stage generally concentrates on:

Diet → adequate fluid → physical activity → a regular lavatory habit

If these are not enough, drug treatment may be used.

Do fibre supplements work?

In some patients, yes.

Soluble fibres such as psyllium in particular may improve stool consistency and bowel regularity.

But fibre does not benefit everyone in the same way.

In people with marked bloating or certain defecation disorders in particular, excessive fibre may increase the complaint.

So “the more fibre the better if you are constipated” is not correct.

Are laxatives harmful?

There is a very strong mistaken belief about this:

“If you use laxatives your bowels become lazy and never work again.”

This statement is not true of all constipation drugs.

There are many drugs for constipation working by different mechanisms.

Osmotic laxatives soften the stool by increasing the amount of water in the bowel. Polyethylene glycol (PEG) is one commonly used example of this group.

Stimulant laxatives may increase bowel movements.

Besides these there are prescription drugs that regulate bowel fluid secretion or motility.

Which drug is suitable varies with the type of constipation and the patient’s characteristics.

What is biofeedback treatment?

It is an extremely important treatment in patients with a pelvic floor or defecation disorder.

With the help of special equipment and training, the patient relearns which muscles to relax and which to use during defecation.

In these patients biofeedback may be a far more appropriate treatment than simply increasing the laxative dose.

The AGA’s 2026 update likewise recommends completing pelvic floor biofeedback treatment in suitable defecation disorders before a patient is regarded as having treatment-resistant constipation.

Is surgery needed for constipation?

Very rarely.

The great majority of people with constipation do not need an operation.

The 2026 AGA recommendations are particularly cautious here: surgery should be considered only in very selected patients in whom slow colonic transit has been objectively demonstrated, a pelvic floor or defecation disorder has been excluded, and serious complaints persist despite other suitable treatments.

In other words, saying only:

“I have been constipated for years.”

is not sufficient grounds for removing the colon surgically.

Is long-standing constipation dangerous?

Most chronic constipation is not due to a serious disease.

But prolonged or severe constipation may lead to problems such as:

• Haemorrhoids,
• Anal fissure,
• Stool hardening and accumulating in the rectum (faecal impaction),
• In some people, overflow leakage of stool.

Liquid stool seeping past hard stool can sometimes be mistaken for “diarrhoea”.

When should a doctor be consulted?

Constipation that is prolonged, recurrent or affecting daily life should be assessed.

A doctor should be seen without delay particularly where constipation is accompanied by:

• Bleeding from the back passage or blood in the stool,
• Unexplained weight loss,
• Persistent or severe abdominal pain,
• Vomiting,
• Fever,
• Inability to pass wind,
• Marked swelling of the abdomen.

Severe abdominal pain + vomiting + inability to pass wind or stool may suggest a condition needing emergency assessment, such as bowel obstruction.

In brief: what people get wrong about constipation

“I must open my bowels every day.” → Wrong. Normal stool frequency varies from person to person.

“Constipation only comes from not drinking enough water.” → Wrong. Constipation has a great many causes.

“The more fibre I eat the better.” → Not always. Fibre helps some patients and increases bloating in others.

“All laxatives make the bowels lazy.” → Wrong. There are different kinds of constipation drug, and the right treatment is chosen for the person.

“If you are constipated you must have a colonoscopy.” → Wrong. The need for colonoscopy is determined by the person’s age, screening status and alarm symptoms.

“If drugs do not help there is nothing to be done.” → Wrong. In resistant constipation, colonic transit and the mechanism of defecation can be investigated; where there is a pelvic floor disorder, treatments such as biofeedback can be used.

Currency: This patient information takes account of the NIDDK’s patient material and the American Gastroenterological Association’s recommendations on the evaluation and management of treatment-resistant constipation, published in January 2026.