Aspirin is commonly recognized as a pain reliever, but in the UK, over two million people take a low-dose version daily, hoping it will safeguard their hearts.

For many years, the 125-year-old medication, known for its blood-thinning properties, was advised for middle-aged and older individuals to prevent heart attacks and strokes, even if they had no previous heart issues.

However, the medical perspective has undergone a significant transformation over the past two decades. Research indicates that for those without existing cardiovascular problems, the benefits of daily aspirin are minimal, while the risks of side effects, such as bruising, stomach bleeding, and rare but severe brain hemorrhages, are considerable.

Estimates from the early 2000s suggest that at the peak of its prescription, aspirin-related side effects may have contributed to approximately 7,000 deaths annually in the UK. This has led to more stringent medical guidelines.

In 2021, official recommendations were revised to suggest that daily low-dose aspirin should be taken only under a doctor’s advice. By 2023, health authorities proposed an even stricter stance, advising against routinely prescribing aspirin for the prevention of initial heart attacks.

The NHS continues to recommend low-dose daily aspirin for patients who have already experienced a heart attack or stroke, as the advantages for these individuals surpass the associated risks.

However, The Mail on Sunday has learned that many healthy patients who haven’t had one of these serious life-threatening events have still not been warned about the potential risks of taking aspirin regularly – a drug that is available in supermarkets and chemists and widely prescribed on the NHS.

Earlier this month, Dr Ellie Cannon, this newspaper’s resident GP columnist, wrote that she continues to see patients who believe they should be taking daily aspirin to protect their heart.

It’s a belief even held by US President Donald Trump, who says he takes 325mg of aspirin every day – three times the standard 75mg dose that was previously recommended. Mr Trump has also blamed the much-discussed large bruises on the backs of his hands on his daily aspirin, and it’s a known side effect.

In response to Dr Cannon’s comments, we received letters and emails from readers who had suffered horrific side-effects as a result of aspirin.

One 72-year-old woman, who took a 75mg daily dose of aspirin for several years on the advice of her GP, told how, while on a cruise ship, she developed severe stomach pains and vomited blood. She quit the aspirin and has had no stomach issues since. And a 73-year-old man was hospitalised with a severe stomach bleed after taking aspirin daily for five years.

Experts are now calling on GPs to warn patients against taking a daily aspirin unless necessary.

So what are the risks of aspirin? And when should you take it?

Aspirin was invented in the 1890s. The drug is based on a compound called salicin, found in willow bark, which had been used by the Ancient Egyptians as a cure for pain and fever. However, it wasn’t until the 1960s that it was discovered that aspirin might help combat heart attacks and strokes – which, known collectively as cardio­vascular disease, lead to around 175,000 UK deaths every year.

Researchers found that the low-dose 75mg tablet worked as a blood thinner, or antiplatelet, that reduces the risk of life-threatening blood clots forming.

This anti-clotting effect appeared to be most effective in the tiny blood vessels in the heart and the brain, making the tablet an excellent and inexpensive preventative treatment. At its most popular, in the early 2000s, this treatment, known by GPs as a ‘junior aspirin’ or ‘baby aspirin’, was being taken daily by nearly a quarter of older Britons.

However, since 2009, baby aspirin prescriptions have fallen markedly following a series of studies that raises concerns about the drug. These studies found that, over time, aspirin can irritate the stomach lining, raising the risk of internal bleeding and dangerous stomach ulcers.

Other studies suggested that aspirin could raise the risk of life-threatening brain bleeds.

This is because its anti-clotting effect, while beneficial for stopping heart attacks and strokes, hindered the body’s ability to stem bleeds – such as after a head injury.

In 2019, one of the largest studies into low-dose aspirin, carried out by the UK’s National Heart And Lung Institute, concluded that for those with no underlying heart problems, the cardiovascular benefits were limited, meaning it prevented fewer heart attacks and strokes than once thought.

The study, published in the Journal of the American Medical Association, also found regularly taking aspirin raised the risk of serious internal bleeding.

Experts say that for the majority of patients there are much more effective, and safe, ways to reduce the risk of cardiovascular disease. ‘For patients who’ve suffered a heart attack or stroke in the past, then there’s still a good argument for taking daily aspirin,’ says Prof Malcolm Finlay, a consultant cardiologist at Barts Heart Centre in Central London. ‘But, for everyone else, there’s very little benefit.

‘When aspirin was first used to prevent cardiovascular disease in the 1970s, it was one of the best drugs for this purpose.

‘Today we have specialist drugs, such as blood pressure tablets and statins for cholesterol, that are much more effective. And all the evidence shows that exercise and a good diet are also more powerful tools than aspirin, and without any of the side-effect risks.’ However, Prof Finlay says many patients are still unaware of the risks of aspirin.

I see a lot of patients left by their doctor on aspirin for a long time,’ he says. ‘These side effects are no joke. You could have a bleed in the stomach, which can be a horrid few days of pain. Or, if the bleed happens in the brain, that could be life-threatening.’

Prof Finlay adds that he has suffered aspirin side effects in the past, after he took the tablet while at university to treat a back injury brought on by rowing. ‘I developed a major stomach bleed,’ he says. ‘So I know firsthand the risk.’

Even for patients who take the drug following cardiovascular issues, aspirin can have serious consequences. Jane Whelan, 74, from Cornwall, began taking 75mg of aspirin daily after suffering a mini-stroke – where a clot temporarily blocks a blood vessel in the brain – in 2012.

She continued to take it until October 2023 when her husband, Peter, 76, woke in the night to find her lying on the floor. ‘She told me she felt sick,’ says Peter. ‘Then she started to vomit blood.’

He called for an ambulance, and scans revealed Jane had a burst stomach ulcer that had led to severe internal bleeding. ‘We spent the next couple of hours watching doctors desperately fighting to save her life,’ says Peter. ‘She needed blood – and a lot of it – quickly. There were whole bags of blood pumped into her to keep her alive.’

Thankfully, Jane’s condition stabilised and, a week later, she was discharged.

Peter says doctors believed Jane’s daily aspirin was the most likely cause of the bleed. ‘She’d developed a number of stomach ulcers in the decade she took the aspirin – this was just the most severe,’ he says.

‘Afterwards, her GP decided she should stop taking the aspirin, and she’s not had any stomach problems since.’

Not all experts agree with the NHS decision to restrict access to daily aspirin. Professor Peter Elwood, an epidemiologist at Cardiff University, says that, while aspirin raises the risk of bleeds about 50 per cent, these bleeds are rarely life-threatening.

‘This is a simple and inexpensive drug that has clear benefits,’ he says. ‘Yes, it can trigger bleeds, but there’s no strong evidence that aspirin kills people.’

Prof Elwood also points to research that suggests that aspirin may even help against cancer.

A 2021 review, which analysed 118 studies, found that patients with cancer who take aspirin are around 20 per cent more likely to survive the disease.

However, experts say that it is still unclear why aspirin has this effect. Moreover, for most patients, the risk of getting a stomach bleed – which, for some can be severe – as a result of aspirin appears to be higher than that of developing cancer.

For patients with existing cardio­vascular problems who are concerned about taking aspirin, there are other blood-thinning medicines such as warfarin or rivaroxaban, that are just as effective.

And, for those who are told that aspirin is necessary, there are ‘gastro-­resistant’ varieties available at pharmacies that are thought to be less damaging to the stomach.

However, Prof Finlay argues that GPs need to do more to warn healthy patients of the risks of taking aspirin.

He also points out that, often, GPs prescribe the tablets omeprazole or lansoprazole alongside aspirin to counteract the side effects. These drugs are design to protect the stomach lining by reducing acid levels.

However, there is growing evidence that suggests that taking these anti-acid drugs long-term raises the risk of stomach infections and bone fractures.

‘Aspirin and anti-acid drugs like omeprazole should not be taken long term,’ says Prof Finlay.

‘There’s a reason why the NHS doesn’t recommend using aspirin in this way any more.

‘We have much better cardio­vascular treatments that don’t have these negative effects.’

Readers’ letters: How aspirin affected you

I have been taking one aspirin daily since I was diagnosed with angina in 2005. Since then I developed three stomach ulcers. I ask my GP at each annual review if I should come off it, but the answer is always no.

Ian Mitchell, 78, from Cambridge

My doctor said taking 75mg of aspirin [a day] would be a good idea. I was on a cruise and I woke up in the night with stomach pains. I began to vomit blood. I went to the ship hospital and was there for three days. I haven’t taken aspirin since.

Shirley Hagger, 72, via email 

I was put on aspirin in 2003 because my GP said I had high blood pressure so was at risk of a heart attack or stroke.

For years I suffered with terrible stomach pains and indigestion. I told my GP but he repeatedly dismissed my concerns.

Then, in 2023, I tripped and hit my head. When I went to the hospital, they found out that I had a severe brain bleed and had to undergo surgery.

I was told afterwards that the aspirin most likely made my brain bleed worse. I’m lucky to be alive.

Stuart Bailey, 78, from Fleet 

I’ve attempted to take enteric-coated low-dose aspirin [also known as gastro-resistant, a type designed to protect the stomach lining] in the past.However, the results are always the same – after a few days I start to get stomach pains.

Mary Berrill, 66, via email

I was told to take two aspirin every day after my triple bypass op ten years ago. About five years ago I had a serious stomach bleed and ended up in A&E. I’ve since gone down to one tablet a day and haven’t had any problems.

John Humphries, 78, via email

My husband is 88 and has suffered mini-strokes in the past. He’s been taking aspirin for a few years now and has recently started to develop stomach problems.

He gets regular diarrhoea, constipation and tummy pains. I’m worried it could be the aspirin but his GP won’t listen to our concerns.

Joyce Warren, 84, from Cardiff

I started taking aspirin about five years ago.

However, I’ve found that I have a bad reaction it. It causes me to bruise. I’ve stopped taking it every day as a result and just take three a week now.

Iris Mcnally, 81, from Cheshire

Two years ago I suffered a slipped disc in my back while gardening. I began taking 75mg of aspirin every day to help with the pain. Then, two weeks later, I suffered a big rectal bleed and was admitted to hospital overnight.

Thankfully the bleeding stopped. The doctors said that the aspirin was the most likely cause.

Edward Lury, 76, from Norfolk