Every time we travel, I do a version of the same pharmacy dash. The kids’ Calpol goes in first, then the plasters, the antihistamine, the travel sickness tablets.
*This is a collaborative post
And then, without much thought, in goes the Prilosec — the little blister pack of omeprazole I have been quietly popping for longer than I probably should admit. Heartburn is one of those things you manage in the background. You do not really think about it. You just grab the box.
It was not until we came back from a two-week trip and I started feeling genuinely rough — headachy, crampy, not quite right — that I actually sat down and read the information that had been sitting inside that packet the whole time.
Table of Contents
What Omeprazole Actually Does
Omeprazole is a proton pump inhibitor, or PPI. That sounds more dramatic than it is. Essentially, it works by blocking the pumps in the lining of your stomach that produce acid. It is incredibly effective at doing this — studies show that a single daily dose can inhibit acid production by up to 100% in some people within the first few hours, with the full suppressive effect building over four days of regular use. The relief is real, and for conditions like GERD, gastritis and ulcers, it can make a huge difference to daily life.
But there is a detail baked into how this drug works that matters when you are taking it casually, on holiday, without a lot of thought.
Because it is not like paracetamol. It does not simply arrive and then leave. When you stop taking omeprazole, your stomach does not just return to where it was before. It can temporarily overshoot, producing more acid than your baseline, not less — a phenomenon known as rebound acid hypersecretion. Research published in Gastroenterology found marked rebound acid hypersecretion after a two-month course of omeprazole, particularly in people who do not have a Helicobacter pylori infection. That burning feeling you get when you run out on the last night of a holiday and then feel worse than ever on the flight home? It may not be the airline food.
The Side Effects Nobody Mentions at the Pharmacy Counter
This is where I want to be genuinely useful, because the leaflet inside the box is a lot to parse when you are also trying to remember which bag the factor 50 is in.
There is a detailed breakdown of omeprazole’s side effects that covers everything from the common and mild — headaches, nausea, gas, stomach pain — to the more serious ones that tend to emerge from long-term or high-dose use. Most people taking it for a short trip will be absolutely fine. But if you are someone who has been reaching for it regularly for months or years, there are a few things that are worth knowing.
The first is magnesium. Long-term PPI use is associated with low magnesium levels, and the symptoms of magnesium deficiency can be genuinely confusing to identify: muscle cramps, irregular heartbeat, fatigue, tremors. Research published in the European Journal of Epidemiology found that low serum magnesium is linked to a significantly increased risk of bone fractures, which compounds another known risk of long-term PPI use — impaired calcium absorption. The NHS Greater Glasgow and Clyde Medicines team, acting on MHRA guidance, now explicitly advises that clinicians should consider checking magnesium levels before and during PPI therapy, particularly in patients with additional risk factors.
The second thing is vitamin B12. Stomach acid is how your body releases B12 from food. Reduce the acid long enough, and absorption drops. This typically takes three or more years of daily use to become an issue, so it is not something to panic about for a fortnight in Tenerife. But if you have been on omeprazole continuously for years without a review, it is worth a conversation with your GP.
What Changes on Holiday and Why It Matters
Here is something practical that got me. Omeprazole works best when taken 30 minutes before your first meal of the day. The NHS guidance on how and when to take omeprazole is clear on this: once a day, first thing in the morning. The reason is mechanical — the drug works by blocking active proton pumps, and those pumps are most active when you are about to eat. Take it after breakfast, and you catch fewer of them.
On holiday, breakfast is not at 7am. Breakfast is when you eventually surface from the kids’ room, negotiate who gets the last croissant and find yourself eating at 10am after a swim. The timing slips. The effectiveness slips with it. If you are wondering why your heartburn is worse on holiday despite taking your medication, inconsistent timing is very often the reason.
Add to that the foods that typically feature on a family holiday — poolside chips, late dinners with wine, citrus-heavy breakfasts, anything fried — and you are consistently giving your stomach acid more to do at exactly the moments your medication is working least efficiently.
The Bit About Stopping That I Did Not Know
If you have been taking omeprazole for a significant stretch of time, you cannot just leave it at home one holiday and see how you get on. The NHS advises that anyone who has been on it long term should speak to a GP before stopping, specifically because of the risk of the stomach producing excess acid when the medication is withdrawn. It is not about being dependent in the way we talk about other substances — it is a physiological response. The body gets used to suppressed acid production, and removal of that suppression causes a temporary spike.
This is why so many people try to come off PPIs and conclude they definitely still need them, when actually they are experiencing a rebound effect that lasts a few weeks and then resolves.
The Interaction You Need to Check Before You Travel
One thing that is easy to forget when packing your holiday medications alongside each other: omeprazole interacts with several common drugs. Blood thinners including warfarin need monitoring when combined with omeprazole, as it can alter how quickly they are metabolised. It also interacts with clopidogrel, the antiplatelet medication often taken after cardiac events — the guidance is that these two should not be taken together at all.
If you are on any regular prescription medication and you routinely take OTC omeprazole, it is worth confirming those two things do not have an interaction you have never thought to check.
What to Do Instead of Just Packing It Automatically
None of this is to say omeprazole is a bad medication. Taken correctly, for appropriate reasons and for a defined period, it does exactly what it should. But the fact that it is available over the counter makes it easy to treat it as a harmless top-up rather than a genuine drug with a mechanism, a duration and a set of effects worth understanding.
If heartburn is a consistent travel companion, it is worth thinking about the foods you eat in the 48 hours before and during the trip — alcohol, caffeine and fatty foods all stimulate acid production and blunt the drug’s effect. Sleeping with your head elevated genuinely helps, particularly on long-haul flights. And if you have been on omeprazole without a proper review in over a year, that is a conversation to have with your GP before the next holiday, not after.
I am still taking mine. But I know a great deal more about what it is actually doing, which means I am taking it on time, not assuming it covers a full evening of tapas and wine, and not just grabbing the next box because the last one ran out.
Pack it. But know what you are packing.
