Constipation is one of the most common reasons adults walk into a UK community pharmacy. The counter options divide cleanly into four classes — bulk-forming, osmotic, stimulant and stool softener — and the right first-line choice depends on whether the stool is hard, infrequent, or both, and whether fluid intake and fibre have already been addressed.
NICE CKS on constipation and the BNF treatment summary shape the advice most UK pharmacists give. This article is the pharmacy counter conversation, turned into one readable guide.
Lifestyle first — always
Before any medicine, UK pharmacists are taught to check three things: fibre intake, fluid intake, and activity level. NICE CKS recommends a minimum of 30 g of fibre a day for adults (from fruit, vegetables and wholegrains) and adequate fluid. Many counter consultations end here, not with a medicine.
The four classes at a glance
| Class | UK examples | Typical onset | Best for |
|---|---|---|---|
| Bulk-forming | Ispaghula husk (Fybogel), methylcellulose, sterculia | 2 to 3 days | Ongoing mild constipation with adequate fluid intake |
| Osmotic | Macrogol 3350 (Laxido, Movicol), lactulose | 1 to 3 days | Hard, infrequent stools; preferred when softening is the goal |
| Stimulant | Senna, bisacodyl, sodium picosulfate | 6 to 12 hours | Short-term use; opioid-induced constipation in combination |
| Stool softener | Docusate sodium, glycerol suppositories | Variable | Post-operative; older patients where straining is risky |
Bulk-forming — the default for most healthy adults
Ispaghula husk (Fybogel) is the UK's most commonly sold bulk-forming laxative. It works by increasing faecal mass, which stimulates peristalsis. It needs adequate fluid intake — at least 1.5 L a day according to BNF — and should not be used in suspected bowel obstruction or where swallowing is difficult. A pharmacist will usually refuse to supply for anyone on opioids without osmotic cover, because bulk-forming agents can worsen opioid-induced constipation.
Osmotic — the workhorse when stools are hard
Macrogol 3350 (sold as Laxido, Movicol and store-own equivalents) has become the default UK osmotic choice. It pulls water into the bowel, softens stool, and is licensed from age 2. Lactulose is still commonly used, particularly in children and pregnancy, but can cause significant bloating.
A community pharmacist will often suggest macrogol when the stool is described as hard, infrequent or causing straining, especially in an older patient.
Stimulant — short-term rescue
Senna and bisacodyl work by direct action on the bowel wall. NICE CKS recommends them as add-on therapy when softening alone is insufficient, or as short-term rescue. Long-term daily stimulant use is discouraged — not because of the old and largely debunked idea of a "lazy bowel," but because it is typically a sign that the underlying problem has not been addressed.
Pharmacies will usually cap sale of stimulant laxatives to small pack sizes if there is any suggestion of misuse, for example in suspected eating disorder presentations. This is a GPhC professional responsibility.
Stool softeners and suppositories
Docusate sodium is a softer option used where straining is medically risky (recent surgery, haemorrhoids, cardiac risk). Glycerol suppositories are fast-acting (within 30 minutes), local, and useful for impaction when oral routes have not worked. Phosphate and sodium citrate enemas are also available; most pharmacies will refer to a GP before supplying.
When the pharmacy refers on
NICE CKS lists clear red flags for onward referral:
- Rectal bleeding that is new or unexplained
- Unintentional weight loss
- Change in bowel habit over the age of 50
- Persistent abdominal pain
- A family history of bowel or ovarian cancer
- Faecal loading in a frail older patient
- Constipation after recent surgery, childbirth, or a medication change the pharmacist cannot review
In these situations the pharmacist will refer to the GP rather than dispense a laxative. Constipation is not currently one of the seven Pharmacy First conditions in England.
Chronic constipation — when a GP has to take over
Persistent constipation over several weeks, or constipation that has not responded to two to four weeks of appropriate laxative therapy, is a GP-led problem in UK practice. NICE CKS is clear that chronic constipation needs assessment for underlying cause (medication side effect, hypothyroidism, diabetes, inflammatory bowel disease, irritable bowel syndrome) rather than escalating doses from the pharmacy shelf.
Prokinetic prescription medicines (prucalopride, linaclotide) are reserved for chronic constipation meeting specific criteria and are prescribed by GPs rather than pharmacy-supplied.
How pharmacies fit the wider care pathway
UK community pharmacies handle the majority of first-presentation constipation without escalation, freeing GP time for the cases that genuinely need assessment. The PharmSee pharmacy finder can be used to locate a local pharmacy, and the salary data gives a sense of the clinical community pharmacist workforce behind this kind of everyday advice.
Caveats and sources
Class labels, licensed ages and dose intervals quoted are from the BNF and NICE CKS as of April 2026. Individual medicine choice depends on personal history and other medicines being taken; nothing in this article replaces a pharmacist or GP consultation.
Sources: NICE CKS on constipation; NHS patient information on constipation; BNF treatment summary on constipation.