Digestive symptoms

Constipation

Also called: chronic constipation, slow transit constipation

Constipation means hard, dry, infrequent or difficult-to-pass stools. NHS criteria define it as fewer than three bowel movements a week, alongside straining, hard stools (Bristol type 1 or 2), or a sense of incomplete emptying. It affects roughly 1 in 7 UK adults at any given time and is more common in women, older adults, and people on slowing medications.

What is happening

Constipation is the result of stool spending too long in the colon. The longer it stays, the more water gets reabsorbed, and the harder and drier it becomes. The slowing can come from gut movement itself, from pelvic floor problems that make passing the stool hard, or from a mix. Most cases are functional, meaning there is no structural cause.

Common causes

  • Low fibre intake. UK average is 19 grams a day against a recommended 30 grams.
  • Low fluid intake or chronic mild dehydration.
  • Sedentary lifestyle. Movement helps gut transit.
  • Slowing medications: opioids, some antidepressants, iron supplements, calcium-channel blockers, and GLP-1 receptor agonists like Ozempic, Wegovy and Mounjaro.
  • Pregnancy. Up to 40 percent of pregnant women experience constipation across pregnancy, peaking in the second and third trimesters.
  • Hypothyroidism. Underactive thyroid slows the whole metabolism, including the gut.
  • Pelvic floor dysfunction. Muscles do not coordinate properly during defaecation.
  • Stress and changes in routine, especially travel.

The fix order

NICE and NHS guidance suggests trying these in sequence. Each step takes a week or two to work. Avoid jumping straight to laxatives.

  1. Hydration: 2 to 2.5 litres a day, every day. Dehydration is the most common single cause and the cheapest fix.
  2. Soluble fibre: psyllium husk (Fybogel, Metamucil) at 5 to 10 grams a day with extra water. Insoluble fibre alone often makes slow-transit constipation worse.
  3. Movement: 20 to 30 minutes of walking a day stimulates the gastrocolic reflex. This single intervention has decent evidence on its own.
  4. Magnesium citrate or magnesium oxide, 200 to 400 mg before bed (some clinicians recommend up to 600 mg short-term, but discuss with a pharmacist or GP first, especially if you have kidney disease). Pulls water into the colon. Gentlest osmotic option and helps sleep.
  5. Osmotic laxatives like macrogol (Movicol, Laxido). Available over the counter. Safe for longer-term use under guidance.
  6. Stimulant laxatives like senna and bisacodyl. Effective but for occasional use. Long-term daily use can lead to colon dependence.

When constipation is not just constipation

See a GP if any of these turn up alongside the constipation: blood in stool, unintentional weight loss, persistent abdominal pain, vomiting alongside constipation, no bowel movement for four or more days, recent change in bowel habit lasting more than three weeks (especially over age 45), or a strong family history of bowel cancer. These are signs that need clinical assessment rather than self-management.

What does not help

  • Detox teas. Most are senna under another name. They are not a wellness intervention.
  • Cutting all fibre. Sometimes recommended online. It typically makes the underlying problem worse.
  • Coffee enemas. No evidence of benefit. Real risk of harm.
  • Sitting on the toilet for ages with the phone. Pelvic floor strain leads to haemorrhoids and worsens incomplete evacuation.

Common questions

How often should you have a bowel movement?
Anywhere from three times a day to three times a week is within normal range, as long as the form is healthy and consistent for you. The single best indicator of gut health is consistency in your own pattern, not absolute frequency.
Are laxatives safe to take every day?
Bulk-forming laxatives like psyllium and osmotic laxatives like macrogol are generally safe for longer-term use under GP guidance. Stimulant laxatives like senna are designed for occasional use. Daily long-term stimulant laxative use can cause the colon to rely on them, although the picture is more nuanced than older textbooks suggested.
Why does GLP-1 medication cause constipation?
GLP-1 receptor agonists slow gastric emptying and gut movement on purpose. That is part of how they work for weight loss and diabetes. About 1 in 5 to 1 in 4 users experience constipation at higher doses (around 24 percent on Wegovy at 2.4 mg in the STEP trials, lower for tirzepatide and lower-dose semaglutide). Standard fixes (fluid, fibre, magnesium, movement) work, in that order.
Can stress cause constipation?
Yes, directly. Stress shifts the nervous system away from digestion. Acute stress can speed transit (as in pre-exam diarrhoea); chronic stress more often slows it. Travel constipation is partly stress and routine disruption combined.

Sources