Constipation
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Constipation: Causes, Treatment and When to Worry
What constipation actually means, why stool form matters more than frequency, the order laxatives are used in, and the changes that need assessing rather than treating.
Key fact: Constipation is not defined by how often you go. You can open your bowels every day and still be constipated if the stools are hard, difficult to pass, or leave a sense of incomplete emptying. That definition matters, because it is the one that decides whether treatment is worth trying.
What constipation actually means
Clinically, constipation is defecation that is unsatisfactory because of infrequent stools, difficult stool passage, or a sense of incomplete emptying. Any one of those three counts. Most people only recognise the first, which is why constipation is both over-diagnosed by people watching the calendar and under-diagnosed by people who go daily but strain every time.
Chronic constipation means symptoms that have been present for months rather than days. That distinction matters because the approach differs: an acute episode usually has a cause you can name — travel, dehydration, a new medicine, a period of inactivity — while a chronic pattern needs a longer view and often needs a cause looked for.
How often is normal
Normal spans roughly three times a day to three times a week. Within that range, frequency alone tells you very little. What tells you more:
- Is it a change from your own normal? Going from daily to twice a week is more meaningful than always having gone twice a week
- Do you strain? Straining more than a quarter of the time is a marker of constipation regardless of frequency
- Does it feel finished? A persistent sense that something is left behind is one of the defining features
- What is the stool like? Hard, lumpy, pellet-like or painful to pass
A persistent change in bowel habit lasting six weeks or more, particularly over the age of 50, is a reason to be assessed — not a reason to buy a stronger laxative. See when constipation is not just constipation.
Reading the stool, not the calendar
The Bristol Stool Chart describes seven stool types. Types 1 and 2 — separate hard lumps, or lumpy and sausage-shaped — indicate constipation. Types 3 and 4, a soft sausage or snake, are the target. Types 6 and 7 are diarrhoea.
Using stool form rather than frequency is the single most useful shift in thinking, because it is what laxative treatment is actually titrated against. The aim is not a bowel movement every day; it is a soft, formed stool passed without straining.
One exception worth knowing now: if you have watery diarrhoea or soiling alongside a feeling of being blocked up, that can be overflow around impacted stool rather than genuine diarrhoea — and taking something to stop the diarrhoea makes it considerably worse. Faecal impaction and overflow soiling covers it.
Why it happens
Most constipation is functional — no structural disease, just a combination of factors slowing transit or making stool harder to pass.
Not enough fibre
UK adults are advised to aim for around 30g of fibre a day. Most eat closer to 20g.
Not enough fluid
Extra fibre without extra fluid makes stools harder, not softer. The two work as a pair.
Inactivity
Bed rest, illness, a desk-bound period or reduced mobility all slow transit.
Ignoring the urge
Repeatedly postponing — at work, while travelling, in an unfamiliar toilet — blunts the reflex over time.
Routine disruption
Travel, shift work and time zone changes are among the commonest triggers of an acute episode.
Pelvic floor problems
Difficulty coordinating the muscles that let stool out, which produces straining despite soft stool.
Medicines that cause it
Drug-induced constipation is common and frequently missed, because the medicine was often started for something else months earlier.
| Group | Examples |
|---|---|
| Opioid painkillers | Codeine, dihydrocodeine, tramadol, morphine — the most predictable cause of all, and it does not wear off with time. See opioid-induced constipation |
| Iron supplements | Ferrous sulfate and similar |
| Anticholinergic and antimuscarinic medicines | Tricyclic antidepressants, some antipsychotics, bladder antimuscarinics, some antihistamines |
| Calcium channel blockers | Verapamil in particular |
| Calcium and aluminium salts | Including some antacids and calcium supplements |
| 5HT₃ antagonists | Ondansetron and related anti-sickness medicines |
Do not stop a prescribed medicine yourself. Some can be swapped, some can be dose-adjusted, and some need to stay with a laxative added alongside. The useful step is to raise it, with a list of what you take, rather than to guess.
Conditions that cause it
- Hypothyroidism — often with fatigue, cold intolerance and weight gain
- Diabetes, particularly with longstanding nerve involvement
- Raised calcium in the blood
- Neurological conditions — Parkinson's disease, multiple sclerosis, spinal cord injury or compression
- Irritable bowel syndrome — specifically the constipation-predominant type, IBS-C, where constipation comes with abdominal pain that eases after opening the bowels
- Pregnancy — hormonal slowing plus iron supplements plus pressure from the uterus. See constipation in pregnancy
- Bowel obstruction or a narrowing — uncommon, but the reason persistent unexplained constipation is investigated rather than simply treated
What to change first
| Change | Why, and how to do it |
|---|---|
| Build fibre gradually | Towards 30g a day, over weeks rather than days. Adding a large amount at once causes bloating and wind and is the commonest reason people give up. Oats, wholegrains, pulses, fruit with skins, linseed. |
| Increase fluid alongside it | This is not optional. Fibre works by holding water; without the water it bulks without softening. |
| Move | A daily walk is enough to matter. Physical activity is one of the more reliable non-drug measures. |
| Go when you need to go | Do not postpone. The urge passes and the stool dries further while it waits. |
| Use the natural window | The bowel is most active in the 30 minutes after a meal, particularly breakfast. Allowing unhurried time then works better than trying at a convenient hour. |
Some fruits contain sorbitol, which draws water into the bowel — apples, apricots, grapes, raspberries, strawberries, and prunes most of all. It is a genuinely useful food effect rather than folklore.
Toilet posture and routine
Sitting with the knees above the hips, feet on a low footstool, straightens the angle the stool has to negotiate and reduces the need to strain. It is a small change with a disproportionate effect, and it costs nothing.
- Feet supported, knees above hips, leaning forward with elbows on knees
- Do not hold your breath and bear down. Breathe out steadily instead; bracing raises pressure without helping the outlet open
- Do not sit for long periods. If nothing is happening after a few minutes, get up and come back later — prolonged sitting and straining contribute to haemorrhoids
- Leave the phone outside. It is the commonest reason people sit for fifteen minutes
Laxatives: the order they are used in
Laxatives are used in a sequence, not chosen at random. The order follows from what is actually wrong with the stool.
| Step | Class | Used when |
|---|---|---|
| 1 | Bulk-forming — ispaghula husk | First line for most people. Needs plenty of fluid alongside. Not for opioid-induced constipation |
| 2 | Osmotic — macrogol, or lactulose | Add or switch if stools remain hard. Macrogol is generally preferred |
| 3 | Stimulant — senna, bisacodyl | Add if stools are soft but still difficult to pass, or emptying feels incomplete |
| 4 | Suppositories and enemas | Where the problem is at the outlet, or oral treatment has not worked |
Most laxatives work within about three days. The dose is titrated against stool form, and treatment is reduced gradually rather than stopped abruptly. Laxatives compared sets out each class in full, and the macrogol guide covers the one people most often take incorrectly.
How long treatment should last
For an acute episode, a short course is enough, and improvement is usually noticeable within a few days. For chronic constipation, treatment often continues for weeks or months, and the dose is reduced gradually once bowel movements have been comfortable and regular for a period — typically after two to four weeks of stability.
Stopping abruptly is the commonest reason for a relapse that gets blamed on the laxative "not working" or on becoming "dependent". Bulk-forming and osmotic laxatives are not habit-forming in that sense.
What happens if it is left
- Haemorrhoids and anal fissures — straining against hard stool is the direct cause of both. An anal fissure then makes people avoid opening their bowels, which worsens the constipation, which worsens the fissure
- Faecal impaction — stool becoming too hard and too large to pass, sometimes with overflow leakage around it
- Bloating and abdominal discomfort — a loaded colon takes up room and gives bacteria longer to ferment, which is why constipation is the most treatable cause of bloating
- Urinary symptoms — a full rectum can press on the bladder
- Reduced quality of life — chronic constipation is consistently underestimated in how much it affects daily life
When it needs assessing
Arrange assessment rather than self-treating if you have: a persistent change in bowel habit lasting six weeks or more, particularly if you are over 50; rectal bleeding; unexplained weight loss; a lump in the abdomen or back passage; persistent tiredness that could be iron deficiency anaemia; stools that have become noticeably narrower; constipation that does not respond to treatment; or a family history of bowel cancer or inflammatory bowel disease. Seek same-day help for severe abdominal pain with vomiting and inability to pass wind, which can indicate obstruction.
Constipation alongside other conditions
- IBS — if constipation comes with abdominal pain that eases after opening your bowels, IBS-C is the likelier label, and fibre needs handling differently. See fibre and IBS, and IBS red flags
- Bloating — frequently the presenting complaint when constipation is the actual problem
- Haemorrhoids — the most common consequence, and treating the constipation is what stops them recurring
- Pelvic floor dysfunction — suspected when someone strains despite soft stool; treated with physiotherapy rather than more laxative
Where to go next
If constipation comes with abdominal pain that eases after opening your bowels, the IBS condition guide is the better starting point, and IBS treatment options set out what is available. For constipation with bleeding or a persistent change in habit, arrange an assessment rather than starting treatment.
Frequently Asked Questions
How do I know if I am constipated?
Constipation means unsatisfactory defecation because of infrequent stools, difficult passage, or a sense of incomplete emptying. Any one of the three counts, so you can open your bowels daily and still be constipated if you strain or never feel finished. Stool form matters more than frequency: hard, lumpy or pellet-like stools indicate constipation.
How often should you poo?
Anywhere between three times a day and three times a week is within the normal range. Frequency alone tells you little. What matters more is whether it has changed from your own normal, whether you strain, whether it feels finished, and what the stool is like.
What is the best laxative for constipation?
There is no single best one; they are used in sequence. A bulk-forming laxative such as ispaghula husk is first line for most people, with plenty of fluid. If stools stay hard, an osmotic laxative is added or substituted, with macrogol generally preferred. If stools are soft but still hard to pass, a stimulant such as senna is added.
How long does it take for constipation to clear?
Most laxatives work within about three days, and lifestyle changes may take a few days to a few weeks to show an effect. Chronic constipation often needs treatment for weeks or months, with the dose reduced gradually once bowel movements have been comfortable and regular for two to four weeks.
When should I worry about constipation?
Get assessed if you have a persistent change in bowel habit lasting six weeks or more, especially over 50, or any rectal bleeding, unexplained weight loss, an abdominal or rectal lump, persistent tiredness, narrower stools, or constipation that does not respond to treatment. Severe abdominal pain with vomiting and inability to pass wind needs same-day help.
Can constipation cause bloating?
Yes, and it is the most common reversible cause. A loaded colon takes up space, slows transit and gives gut bacteria longer to ferment, which produces a larger, tighter abdomen. Treating the constipation often resolves the bloating.
References
- NHS. Constipation. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Constipation. cks.nice.org.uk
- Electronic Medicines Compendium. Movicol 13.7g powder for oral solution: Summary of Product Characteristics. medicines.org.uk
- National Institute for Health and Care Excellence. Suspected cancer: recognition and referral (NG12). nice.org.uk
- National Institute for Health and Care Excellence. Quantitative faecal immunochemical testing to guide referral for colorectal cancer in primary care (DG56). nice.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. A persistent change in bowel habit, rectal bleeding or unexplained weight loss should always be assessed rather than treated as constipation. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.
