Seven common causes of constipation

Constipation is a common bowel condition, with around one in seven adults in the UK experiencing constipation at any given time. It occurs when you’re unable to completely empty your bowels or you’re passing stools less often than is usual for you. 

As a general rule, opening your bowels anywhere from three times a day to three times a week is considered healthy. It is, therefore, important to note what frequency of bowel movements is normal for you. If you’re passing stools less often, you may be constipated.

Symptoms of constipation

In addition to a reduced frequency of bowel movements and/or an inability to completely empty your bowels, constipation may cause you to strain when passing stools. 

Your stools may become lumpy, dry and/or hard, as well as reduced in volume. You may also experience abdominal pain, cramps, bloating, nausea and loss of appetite. 

Are you at risk of constipation?

Most people experience constipation at some point in their lives and it can occur at any age. However, constipation is twice as likely to occur in women, particularly pregnant women, and is also more common in older people. 

Your risk of constipation is higher if you’re overweight or underweight, have a mental health condition, such as anxiety or depression, have certain other health conditions and/or are taking certain medications. 

Seven common causes of constipation

1. A low-fibre diet 

Dietary fibre refers to substances found in plants that your body can’t completely break down. Consequently, dietary fibre passes into your large bowel relatively unchanged, where it helps retain water in your stools, making them softer and bulkier. A diet low in dietary fibre, therefore, makes your stools harder, which increases your risk of constipation.  

Dietary fibre can be found in whole grains (eg whole wheat pasta and brown rice), fruits, vegetables, potato skin, nuts, seeds and pulses (eg lentils, black beans and split peas). 

2. A change to your routine and/or eating habits

Your bowel habits are affected by your daily routine and your body’s internal clock, which is regulated by several different hormones. Consequently, a change in your routine, such as starting a new job, staying up through the night or being unable to exercise due to an injury or ill health, can increase your risk of constipation. 

A change in routine is often accompanied by a change in your eating habits, which also increases your risk of constipation, for example, if you go on holiday or start a new diet that is low in fibre. 

3. A less active lifestyle

Regular exercise helps prevent your stools from becoming lumpy, dry and/or hard. This is because of how your stools are made. 

Your stools are what remains from the food you eat. As digested food passes through your bowels, nutrients and water are absorbed from the food into your body. The slower the digested food moves through your bowels, the more water is absorbed — this makes your stools drier and harder. 

Movement and exercise help the muscles in your abdomen move food faster through your bowels. A less active lifestyle makes these muscles weaker so digested food moves more slowly through your bowels, increasing your risk of constipation. 

4. Not drinking enough fluids

To ensure your body stays hydrated it’s important to drink, on average, 1.5–2.5 litres of hydrating fluids every day, which is about equivalent to six to eight cups. However, if you’re sweating, you will need to drink more to stay hydrated. 

If you don’t drink enough fluids, your body will draw more fluid out of your digested food as it passes through your bowels. This will make your stools harder, causing constipation. 

5. Suppressing the urge to open your bowels

The urge to open your bowels is usually strongest after eating — this is called the gastrocolic reflex. It is particularly strong after fasting, which is why many people open their bowels in the morning after eating breakfast. It is important to act on this urge as repeatedly suppressing it increases your risk of constipation. 

Every time you suppress the urge to open your bowels, your stool is pushed back up into your large colon where more water can be absorbed out of it, leading to drier, harder stools. 

6. Health conditions

Several bowel conditions increase your risk of constipation including irritable bowel syndrome (IBS), diverticulitis, bowel cancer and bowel obstruction.

Other health conditions that increase your risk include nervous system conditions, such as Parkinson's disease, multiple sclerosis, stroke and spinal cord injuries, endocrine conditions, such as diabetes, hypercalcemia and hypothyroidism, and systemic conditions, such as amyloidosis, lupus and scleroderma.

7. Medications

Certain medications can cause constipation as a side effect. These include certain strong painkillers (eg codeine), non-steroidal anti-inflammatory drugs (eg ibuprofen), antidepressants, iron tablets and antihistamines. 

Medications that treat high blood pressure (eg calcium channel blockers), psychiatric conditions (eg clozapine), seizures (eg gabapentin) and nausea (eg ondansetron) can cause constipation as a side effect too.  

Overusing laxatives can lead to constipation as the nerves that supply your bowels and the muscles around your bowels can become less responsive. This makes it harder to move stools through your bowels.

When to see a doctor

In most cases, simple dietary and lifestyle changes can resolve constipation. In some cases, you may also need to take over-the-counter medication. If these approaches are unsuccessful, see your GP. 

You should also see your GP if your constipation is accompanied by rectal bleeding, unexplained weight loss and/or persistent fatigue, or if it lasts more than 14 days without signs of improvement. 

How is constipation diagnosed?

Getting a diagnosis of constipation usually involves answering questions about your bowel habits, diet, lifestyle, symptoms and medical history. 

If your doctor is concerned that you may have faecal impaction — where dry, hard stools are stuck in your back passage (rectum) — they may need to perform a physical examination. This involves feeling your abdomen and using a lubricated, gloved finger to feel the inside of your rectum. 

Potential complications of constipation 

Occasional episodes of constipation do not usually cause any complications. However, if you have long-term (chronic) constipation, you may be at risk of other health conditions. This includes rectal bleeding due to repeated straining when you open your bowels — this may be caused by piles (haemorrhoids) or an anal fissure. 

Faecal impaction is also a potential complication of constipation. This usually needs treatment with an oral laxative, suppository or enema. 

Faecal impaction can lead to bowel incontinence, where watery stools above the trapped hard stools in your rectum leak around the hard stools.

Treating constipation

Constipation can usually be effectively treated with dietary and lifestyle changes, such as eating more fibre-rich foods, drinking more water, exercising regularly and keeping to a routine that allows you to go to the toilet when you naturally feel the urge to open your bowels. 

When you’re trying to pass stools, it can help to place your feet on a low footstool, so that your knees are raised above the level of your hips — this aids bowel movement. 

If these approaches aren’t effective enough, you can try taking an over-the-counter oral laxative. 

Laxatives

There are several types of over-the-counter oral laxatives that your local pharmacist can advise you on. 

A bulk-forming laxative (eg ispaghula husk, methylcellulose or sterculia), which helps your stools retain fluid, is usually recommended first. If this isn’t enough to resolve your constipation, your pharmacist may suggest taking an osmotic laxative (eg lactulose or macrogol), which helps your bowels retain more fluid. 

Bulk-forming and osmotic laxatives help soften your stools. However, if you still can’t pass stools, you may need a stimulant laxative (eg bisacodyl picosulphate, senna or sodium picosulphate). This will stimulate the muscles around your bowels to help move your stools along.

Prescription treatments

If diet, lifestyle changes and over-the-counter medication haven’t resolved your constipation, see your GP. 

If you have faecal impaction, they may prescribe a high-dose osmotic laxative for several days followed by a stimulant laxative. 

If these treatments aren’t effective enough, your doctor may prescribe a stimulant laxative in suppository form ie as a round or capsule-shaped object that you insert into your anus. 

Alternatively, they may prescribe a mini-enema, where a liquid osmotic laxative is injected through your anus via a small tube with a nozzle on the end. 

Surgery

If your constipation doesn’t resolve with laxatives or you have other symptoms, such as bleeding or unexplained weight loss, you may need imaging tests of your abdomen to investigate potential underlying causes.

If your results show that you have a blockage or narrowing of your large bowel, surgery may be needed.