Omeprazole and gallstones: what it can and cannot do

Omeprazole is a proton pump inhibitor (PPI). It works by blocking the acid-producing pumps in the lining of the stomach, which lowers the amount of acid your stomach makes.

That makes it effective for acid reflux, gastritis and peptic ulcers - conditions driven by stomach acid.

Gallstones are a different problem entirely. They form in the gallbladder, a small pouch under the liver that stores bile.

Most gallstones in the UK are made of hardened cholesterol; a smaller proportion are pigment stones formed from bilirubin.

Stomach acid plays no part in how they form, so reducing acid with omeprazole does nothing to shrink, dissolve or prevent them.

This matters in practice because the two conditions are frequently confused.

A person with gallstones may be started on omeprazole for presumed indigestion, feel slightly better for a while (PPIs do ease any coexisting acid symptoms), and have the underlying diagnosis delayed by months.

The treatments are also entirely different:

• Gallstones causing symptoms are usually treated with laparoscopic cholecystectomy - keyhole surgery to remove the gallbladder
• Silent gallstones found incidentally on a scan usually need no treatment at all
• Acid-related symptoms respond to omeprazole and lifestyle measures

If you have been told you have gallstones, taking omeprazole will not deal with them - although your doctor may still prescribe it if you also have genuine reflux symptoms alongside.

The overlap between acid-related dyspepsia and gallstone pain is one of the commonest sources of diagnostic confusion in general practice.

Both can cause discomfort in the upper abdomen after meals, but there are useful distinguishing features.

Typical acid reflux or dyspepsia:

• burning sensation rising behind the breastbone (heartburn)
• acidic taste in the mouth, belching, bloating
• discomfort that is worse when lying flat or bending over
• relieved, at least partly, by antacids or omeprazole

Typical biliary colic (gallstone pain):

• sudden, intense pain in the right upper abdomen or the centre of the upper abdomen
• pain that builds over 15 to 60 minutes, stays severe for one to five hours, then fades
• pain radiating to the right shoulder blade or through to the back
• often triggered by fatty meals, and frequently wakes you at night
• nausea or vomiting during attacks
• little or no relief from antacids or PPIs

The pattern over time is telling.

Reflux tends to grumble on most days, varying with meals and posture; biliary colic comes in discrete, severe episodes with completely normal spells in between, sometimes weeks apart.

A key practical clue: if you have taken omeprazole correctly for four weeks - once daily, 30 to 60 minutes before breakfast - and you still get bouts of severe upper abdominal pain, acid is unlikely to be the whole story, and gallstones deserve consideration.

A reasonable question is whether taking omeprazole could affect the gallbladder itself. Research here is limited, and the findings are not conclusive.

Some small physiological studies suggest PPIs may slightly reduce gallbladder motility - how strongly the gallbladder contracts to empty bile after a meal.

Sluggish emptying is one of the factors thought to encourage stone formation.

In addition, a few large observational studies have reported a modest association between long-term PPI use and a higher rate of gallstone disease.

These findings need careful interpretation:

• Observational studies cannot prove cause and effect. People who take PPIs differ from those who do not - they tend to be older, heavier and to have more digestive complaints, all of which independently raise gallstone risk
• The reported increases in risk are small in absolute terms
• Gallstones are not listed as a side effect of omeprazole in the UK Summary of Product Characteristics, and no regulator, including the MHRA, has issued a warning on this point

The practical conclusion is balanced. There is no good evidence that omeprazole causes gallstones, and no reason to stop a PPI you genuinely need out of concern for your gallbladder.

Equally, there is no evidence whatsoever that omeprazole treats or prevents gallstones.

If you have been taking omeprazole for a long time without a clear ongoing reason, that is worth reviewing with your GP in its own right - see our article on long-term omeprazole use for what such a review involves.

If your GP suspects gallstones, the diagnostic pathway in the NHS is well established and usually straightforward.

Abdominal ultrasound is the first-line test. It is painless, takes around 15 to 20 minutes and detects gallstones in the gallbladder with better than 95% accuracy.

You will usually be asked not to eat for about six hours beforehand so the gallbladder is full and easy to see.

Ultrasound can also show signs of inflammation, such as a thickened gallbladder wall, and whether the bile ducts are widened - a clue that a stone may have moved into the duct.

Blood tests are usually taken at the same time:

• liver function tests - raised levels can indicate a blocked bile duct
• full blood count - a raised white cell count suggests inflammation or infection
• amylase or lipase - to check for pancreatitis, a recognised complication of gallstones

Further imaging is needed in a minority of cases. An MRCP - a specialised MRI scan of the bile ducts - is used when ultrasound is normal but suspicion of duct stones remains.

Endoscopic ultrasound is an alternative in some hospitals.

Where does omeprazole fit in? GPs sometimes use a treatment trial of a PPI as part of assessing upper abdominal symptoms.

A clear response supports acid-related disease; a poor response after four weeks at the standard dose makes it more likely that something else, such as gallstones, is responsible - and is a good reason to arrange an ultrasound.

Most gallstone attacks settle on their own within a few hours, but complications can be serious.

Seek urgent medical attention - call NHS 111, or 999 if symptoms are severe - if you develop any of the following.

Signs of acute cholecystitis (inflamed gallbladder):

• constant right upper abdominal pain lasting more than five hours
• fever or shivering
• pain so severe you cannot find a comfortable position

Signs of a blocked bile duct or cholangitis:

• yellowing of the skin or eyes (jaundice)
• dark urine and pale, clay-coloured stools
• itching all over the body
• fever together with jaundice - a medical emergency

Signs of acute pancreatitis:

• sudden severe pain in the centre of the upper abdomen, boring through to the back
• persistent vomiting
• feeling generally very unwell

None of these situations will respond to omeprazole, antacids or painkillers at home - they need hospital assessment, intravenous fluids, antibiotics where appropriate and sometimes an urgent procedure to remove duct stones.

Separately, see your GP soon (not as an emergency) if you have unintentional weight loss, difficulty swallowing, vomiting blood, black tarry stools, or new persistent indigestion for the first time over the age of 55.

These are alarm features that need investigation in their own right, whether or not gallstones turn out to be present.

You cannot dissolve existing gallstones with diet, but sensible measures reduce the chance of painful attacks and may lower the risk of forming new stones.

Manage weight - but lose it gradually. Obesity is one of the strongest risk factors for cholesterol gallstones. However, rapid weight loss - crash diets, or more than about 1.

5 kg per week - paradoxically increases stone formation, because the liver excretes extra cholesterol into bile. Aim for a steady 0.5 to 1 kg per week.

Eat regularly. Long gaps between meals mean bile sits in the gallbladder for hours and becomes more concentrated. Regular meals, including breakfast, keep bile flowing.

Moderate fat rather than avoiding it completely. Very low-fat diets reduce gallbladder emptying.

A balanced Mediterranean-style diet rich in fruit, vegetables, wholegrains and unsaturated fats is associated with lower gallstone risk.

Stay active. Regular physical activity is independently associated with fewer symptomatic gallstones.

If you take omeprazole for reflux, many of the same measures help on both fronts: weight loss reduces reflux, smaller regular meals ease both conditions, and cutting down alcohol benefits the liver and the stomach lining alike.

These steps matter most while waiting for gallbladder surgery - a lower-fat diet during that period reduces the frequency of biliary colic attacks for most people, since fatty meals are the main trigger for gallbladder contraction against a stone.