Proton Pump Inhibitors UK: Dosage, Side Effects & Safety Guide

The definitive UK reference on PPIs — how they work, doses for every condition, side effects, interactions, prices and long-term safety.

Part of the Complete Acid Reflux Guide.

What a proton pump inhibitor is

Proton pump inhibitors are among the most widely prescribed medicines in the world; the UK issues tens of millions of prescriptions a year. A PPI reduces the amount of acid the stomach produces, making it effective for everything from persistent heartburn and GORD to peptic ulcers and Helicobacter pylori infection. They differ from antacids, which neutralise acid already present, and from H2 blockers, which temporarily reduce secretion — a PPI blocks acid production at its source, more completely and for longer. For the mechanism explained simply, see What is a proton pump inhibitor?

How PPIs work in the body

PPIs are inactive when swallowed. Protected by a coating that stops them dissolving too early, they pass through the stomach, are absorbed from the small intestine into the bloodstream, then travel to the stomach’s parietal cells. In the acidic channels inside each cell they convert to their active form and irreversibly bind the H+/K+ ATPase enzyme — the proton pump — blocking that pump for good. A new pump must be built before acid production resumes, which takes 18–24 hours. This is why once-daily dosing works, and why taking a PPI before a meal — when pumps are most active — beats taking it after eating.

PPIs available in the UK

Five PPIs are licensed in the UK. All are available on prescription; lower doses of omeprazole, esomeprazole and lansoprazole are available over the counter for short-term use.

Each of the three main drugs has its own detailed guide: omeprazole, lansoprazole and esomeprazole.

What conditions PPIs treat

• Gastro-oesophageal reflux disease (GORD) — chronic reflux causing heartburn, regurgitation and oesophageal irritation
• Erosive oesophagitis — inflammation and erosion of the oesophageal lining; PPIs are first-line
• Gastric and duodenal ulcers — reducing acid to allow healing
• H. pylori eradication — combined with antibiotics in triple therapy
• Zollinger–Ellison syndrome — rare tumour-driven acid overproduction
• NSAID ulcer prevention — protecting the stomach in people on long-term anti-inflammatories

For how PPIs are used across peptic ulcer disease and H. pylori, see our peptic ulcers & H. pylori guide.

PPI dosage guide

Doses vary by drug and condition. The table gives typical ranges — your actual dose must always come from your prescriber.

When and how to take a PPI

• Take your PPI 30 minutes before breakfast — for most people, first thing in the morning
• If prescribed twice daily, take the second dose 30 minutes before your evening meal
• Swallow with a full glass of water — not juice, milk or coffee
• Swallow capsules or tablets whole; never crush or chew
• If you miss a dose, take it when you remember — do not double up the next day

PPI side effects

Most people tolerate PPIs well, especially on short courses. Side effects are reported in roughly 1–2% of users.

Common (usually first week or two)

• Headache
• Diarrhoea or constipation
• Nausea, stomach discomfort, bloating or wind

Associated with long-term use

• Low magnesium — can cause cramps and palpitations; detectable on a blood test
• Vitamin B12 deficiency — acid helps release B12 from food; long-term suppression can reduce absorption
• Modestly increased fracture risk — small in absolute terms, more relevant with other osteoporosis risk factors
• Gut infections including C. difficile — lower acidity raises susceptibility
• Rebound acid on abrupt stopping after a long course — see below

Stopping a PPI: tapering and rebound acid

Stopping a PPI abruptly after a long course can trigger rebound acid hypersecretion — a temporary surge as suppressed pumps regenerate together, often mistaken for the original condition returning. NICE recommends stepping down: reduce to the lowest effective dose, then on-demand use, then stop, over two to four weeks. Our dedicated guide covers the week-by-week method: Stopping Omeprazole and Other PPIs.

Drug interactions

Also tell your prescriber if you take methotrexate (levels can rise), warfarin (may need more INR monitoring), digoxin, certain HIV medicines (atazanavir, nelfinavir — absorption impaired), or medicines needing stomach acid to absorb, such as itraconazole and iron supplements. Always list everything you take, including supplements, before starting a PPI.

When you need prescription-strength PPIs

PPI prices in the UK

PPIs are among the cheapest medicines in routine use, but what you pay depends entirely on the route:

One money point worth knowing: branded and generic PPIs are the same medicine. Generic esomeprazole costs a fraction of branded Nexium, and generic omeprazole a fraction of Losec — for identical active ingredient and effect. Unless you have a specific reason to prefer the brand, the generic is the sensible choice.

Alternatives to PPIs

• H2 blockers (famotidine) — act within an hour, good for on-demand and night use; see our famotidine guide
• Antacids (Rennie, Tums) — neutralise acid within minutes; short-lived, for occasional heartburn
• Alginates (Gaviscon) — form a raft that physically blocks reflux; see Omeprazole vs Gaviscon
• Lifestyle change — for mild-to-moderate GORD, often as effective as medication; see foods to avoid

Treatment from Access Doctor

Access Doctor’s pharmacist independent prescribers can assess your symptoms and prescribe the right PPI following a short online consultation, with discreet next-day delivery across the UK.