Constipation: NHS-Style Guide to Causes, Relief, and When to See a GP
Bristol Stool Types 1-2 - Updated April 2026
What Is Constipation?
The NHS defines constipation as having fewer than three bowel movements per week, passing hard or lumpy stools, needing to strain to have a bowel movement, feeling as though you cannot fully empty your bowel, or feeling as though there is a blockage in your rectum. Constipation is one of the most common digestive complaints in the UK, affecting around one in seven adults at any one time and up to one in three children.
On the Bristol Stool Chart, constipation typically presents as types 1 or 2 - separate hard lumps or a lumpy, hard sausage. Both indicate that stool has spent too long in the colon, losing excess water through the intestinal wall. The result is hard, dry stool that is difficult and uncomfortable to pass.
Common Causes of Constipation
Self-Care: Fibre, Fluid, and Movement
Dietary Fibre (NHS Target: 30g/day)
The NHS recommends 30g of dietary fibre per day for adults. The UK average is approximately 18g - a significant shortfall. For constipation, soluble fibre is particularly important: it dissolves in water to form a gel-like substance that retains moisture in the stool. Good soluble fibre sources include oats, psyllium husk (available as supplements), ground flaxseed, pulses (lentils, chickpeas, kidney beans), apples, pears, and most root vegetables. Introduce fibre increases gradually over 2-4 weeks to avoid bloating.
Hydration
Aim for 1.5-2 litres of fluid per day. Fibre requires water to work - a high-fibre diet without adequate hydration can actually worsen constipation. Spread your fluid intake through the day rather than drinking large amounts at once. A glass of water first thing in the morning can help stimulate the gastrocolic reflex.
Physical Activity
Regular physical activity accelerates colonic transit. A 30-minute walk per day has been shown in multiple studies to reduce constipation frequency. For desk-based workers, brief movement breaks every 60-90 minutes can make a meaningful difference.
Toileting Position
Elevating your knees above your hips using a toilet stool (placing a small platform under your feet) replicates the physiological squatting position and relaxes the puborectalis muscle, making defecation significantly easier. Several clinical studies have shown this reduces straining and time spent on the toilet.
Laxatives: The NHS Stepwise Approach
All laxatives are available without prescription at UK pharmacies. Always take with adequate fluid. Consult your pharmacist before starting a laxative if you are pregnant, have a chronic condition, or are taking regular medications.
When to See Your GP
- !No bowel movement for more than 7 days despite dietary change and laxative use
- !Blood in or on your stool, or on toilet paper
- !Unintentional weight loss alongside a change in bowel habit
- !New-onset constipation in a person aged over 50, especially with no obvious dietary explanation
- !Abdominal pain, bloating, or vomiting with constipation
- !Constipation alternating with diarrhoea (may indicate IBS-M or underlying bowel condition)
- !Symptoms suggesting bowel obstruction: vomiting, complete absence of wind and stool, severe abdominal distension
- !Family history of bowel cancer and new bowel habit change
For the full NICE suspected bowel cancer referral criteria (NG12, 2-week-wait thresholds), see our Red Flags guide.
Probiotics and Fibre Supplements: What the Evidence Shows
Psyllium husk (sold as Fybogel in the UK) is both a bulk-forming laxative and a prebiotic fibre. It is the most studied dietary supplement for constipation and is recommended by the NHS and NICE. It can improve stool frequency and consistency as effectively as some osmotic laxatives in mild-to-moderate constipation.
For constipation-specific probiotic evidence, Bifidobacterium lactis DN-173010 (found in some commercial probiotic yoghurts) has moderate evidence for reducing transit time in healthy adults with slow transit. Lactobacillus acidophilus NCFM has evidence for bloating reduction. Our partner resource probioticvsprebiotic.com provides a full evidence review.
Updated April 2026