Medicines and your bloods
On Omeprazole Long-Term? The Two Things Worth Checking
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20265 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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If you have taken omeprazole or lansoprazole daily for a year or more, two markers are worth checking: vitamin B12 and magnesium. Stomach acid helps release B12 from food, and the MHRA links long PPI use to low magnesium. A blood test shows your levels. Do not stop your tablet to find out.
See what to check →As of August 2026. Reflux forums are busy again. The question doing the rounds is not whether these tablets work. It is what happens after year three, and whether anyone is keeping an eye on it. A study of nutrient levels in long-term users landed in March 2026 and pushed the topic back into view.
Omeprazole and lansoprazole are proton pump inhibitors, usually shortened to PPIs. They work by turning down the acid your stomach makes. That is the point of them, and for many people they are the difference between sleeping flat and not sleeping at all.
But stomach acid has a second job. It helps pull certain nutrients out of food. Turn the acid down for years and two of those nutrients can drift. This guide covers which two, what the official sources say, and how to check without guessing.
1. Why does a reflux tablet touch your nutrient levels?
It comes down to what acid does before your food ever reaches the gut. Vitamin B12 arrives bound to protein. Acid and an enzyme called pepsin break that bond so the B12 comes free and can be absorbed further down. Less acid means less of it gets released.
Magnesium is a different story. Magnesium is a mineral your muscles and nerves rely on. It is taken up in the small intestine, and long PPI use appears to interfere with that uptake. The mechanism is still argued over. The signal in the safety reports is not.
Two things matter here. The first is time. Neither effect shows up in the fortnight of tablets you took after a bad Christmas. The second is that both are measurable, so you are not left guessing.
2. Vitamin B12: the one the NHS names
The NHS is direct about this on its own omeprazole page. It says the chance of serious side effects goes up if you take omeprazole for a year or more, and it lists B12 among them.
“Having a very low level of vitamin B12, which can cause symptoms such as tiredness, dizziness, or muscle twitches or weakness.”
— NHS, side effects of omeprazole
Read that symptom list again. Tiredness, dizziness, weakness. Those are the things people put down to work, or age, or a bad few months of sleep. They are also exactly what a low B12 feels like.
A 2022 systematic review in Cureus pulled together seven observational studies on this. In one of them, people taking a PPI for two years or more had roughly 1.65 times the odds of a low B12 compared with people who were not. That is an association across a population, not a forecast for you. It is a reason to look, not a reason to worry.
A low B12 also leaves a fingerprint elsewhere. It can make red blood cells unusually large, which shows on a full blood count. Our vitamin B12 blood test guide explains how the number itself is read.
3. Magnesium: what the MHRA told prescribers
This one is less famous, and it is the more interesting of the two. In April 2012 the UK medicines regulator issued formal advice to prescribers about low magnesium in people on long-term PPIs. The advice still stands.
“Consider measurement of magnesium levels before starting PPI treatment and periodically during prolonged treatment.”
— MHRA Drug Safety Update, April 2012
The same notice gives the timing. Reported cases turned up after three months of treatment, but most appeared after a year. It flags a higher risk for people also taking digoxin or a diuretic, which is a water tablet. And it names the things to report: muscle twitches, tremors, vomiting, tiredness and loss of appetite.
Here is the honest gap. That advice went to prescribers fourteen years ago, and in practice the periodic check is not something most people on a repeat prescription are ever offered. If nobody has measured yours, you are in ordinary company. Our guide to the signs of low magnesium covers what a shortfall tends to feel like.
4. What to do about it
Do not stop the tablet. Coming off a PPI suddenly can bring on a burst of rebound acid, which feels worse than what sent you to the pharmacy in the first place. If you want to come off it, that is a conversation with your GP or pharmacist, not a decision to take alone.
Get the two numbers.Vitamin B12 and magnesium are both ordinary blood markers. Knowing them turns a vague worry into something you can act on, or dismiss. Both sit in Helvy's General Energy & Wellness panel (£149), alongside vitamin D, cortisol and thyroid within its 17 markers. It is a home finger-prick kit run by a UKAS-accredited UK lab, with results in around 5 working days.
Read them next to your symptoms. Tiredness has a long list of measurable causes, and a PPI is only one of them. Low iron and an underactive thyroid produce much the same feeling. Our energy and fatigue hub walks through the full set worth ruling out.
One last thing. A blood test measures a level. It does not diagnose anything, and it is not a reason to change a prescribed medicine on your own. If a number comes back low, or a symptom is affecting your day, a qualified clinician is the right next call.
READY TO TEST?
Check your B12 and magnesium at home
The MHRA asked for periodic magnesium checks on long-term PPIs, and the NHS names low B12 as a risk after a year or more. Helvy's General Energy & Wellness panel measures both, within 17 markers, from a finger-prick at home.
Frequently asked questions
Does omeprazole lower your vitamin B12?
It can, over long periods. The NHS lists a very low vitamin B12 among the risks of taking omeprazole for a year or more. Stomach acid helps free B12 from food, so less acid means less is released. A blood test shows where your own level sits.
How long do you have to be on a PPI before it matters?
Roughly a year. The MHRA reported that low magnesium cases appeared after three months of treatment, but most came after a year. The NHS uses the same rough line for omeprazole side effects generally. Short courses of a few weeks are not the concern here.
Should I stop taking omeprazole?
Not on your own. Stopping suddenly can trigger rebound acid, which often feels worse than the original symptoms. NICE recommends the lowest dose that keeps symptoms under control, so a step down is a real option. That is a conversation for your GP or pharmacist.
Which blood test checks B12 and magnesium together?
Any panel that carries both. Helvy's General Energy & Wellness panel measures vitamin B12 and magnesium within its 17 markers, along with vitamin D, cortisol and thyroid. It is a home finger-prick kit, and results come back in about 5 working days.
What are the signs of low magnesium on a PPI?
The MHRA asked patients to report muscle twitches, tremors, vomiting, tiredness and loss of appetite. None of these prove anything on their own, because each has other common causes. That overlap is the reason a measured level is worth more than a symptom list.
Related guides
Vitamin B12 Blood Test UK
What the number means, why symptoms show before a level looks low, and how to read a result.
Magnesium Blood Test UK
Serum vs RBC magnesium, and how to read whether you are actually low.
Tingling & Numbness Blood Test UK
The measurable causes behind pins and needles, from B12 to blood sugar.
Tired All the Time?
The testable causes of low energy, and the markers worth checking before you blame stress.