{"id":9763,"date":"2026-05-26T19:19:08","date_gmt":"2026-05-26T19:19:08","guid":{"rendered":"https:\/\/www.healthoptibody.com\/?p=9763"},"modified":"2026-05-26T19:19:08","modified_gmt":"2026-05-26T19:19:08","slug":"from-mounjaro-to-painkillers-heart-pills-even-hrt-why-some-drugs-will-never-work-for-you","status":"publish","type":"post","link":"https:\/\/www.healthoptibody.com\/?p=9763","title":{"rendered":"From Mounjaro, to painkillers, heart pills, even HRT… why some drugs will NEVER work for you"},"content":{"rendered":"

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Olivia Hillary was over the moon when she was prescribed Mounjaro on the NHS<\/a> to control her type 2 diabetes<\/a>.<\/p>\n

While GLP-1 drugs such as Mounjaro are better known for weight loss<\/a>, they were actually developed for type 2 diabetes and Olivia was desperate to improve her health.<\/p>\n

She had tried \u2018every diet going\u2019 since she began gaining weight at the age of 17. \u2018I\u2019ve joined slimming clubs and tried meal-replacement diets, but nothing worked long term,\u2019 says the 39-year-old mental health nurse.<\/p>\n

Her weight had affected her health, too. By 2023, Olivia weighed 18st (at 5ft 7in she had a BMI of more than 40; over 27.5 is classed as obese), and as well as high blood pressure, she was living with uncontrolled type 2 diabetes.<\/p>\n

\u2018I felt like I\u2019d hit a wall,\u2019 says Olivia, who lives in York with partner Myles, 39, an HGV driver.<\/p>\n

\u2018My medications for diabetes weren\u2019t working, my mood was always up and down and my weight remained high. I didn\u2019t know what else to do \u2013 and the offer of Mounjaro felt like a way out and gave me hope there was a brighter future around the corner.\u2019<\/p>\n

At the time, her HbA1c level \u2013 a measure of the average \u2018sugariness\u2019 of the blood over three months \u2013 was 78mmol\/mol, well above the cut off for type 2 diabetes, which is 48.<\/p>\n

Olivia was also hopeful Mounjaro would help reduce her food cravings and aid weight loss.<\/p>\n

GLP-1 agonist drugs such as Mounjaro and Ozempic work by mimicking glucagon-like peptide-1, a hormone in the body that slows digestion and signals fullness to the brain, silencing \u2018food noise\u2019. As a result, most people feel satisfied quicker and eat less.<\/p>\n

\u2018As someone who was constantly thinking about food \u2013 it felt as if the fridge was always calling \u2013 it sounded like something that might finally switch off that \u201cfood noise\u201d,\u2019 says Olivia.<\/p>\n

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\"By <\/div>\n<\/p><\/div>\n

By 2023, Olivia weighed 18st (at 5ft 7in she had a BMI of more than 40; over 27.5 is classed as obese), and as well as high blood pressure, she was living with uncontrolled type 2 diabetes<\/p>\n<\/div>\n

And she\u2019d seen first-hand what these drugs could do. Myles, who also had type 2 diabetes and a BMI of nearly 40, had lost 5st after being prescribed Ozempic on the NHS and his diabetes had been brought under control.<\/p>\n

Olivia began on weekly 2.5mg Mounjaro injections \u2013 over six months, the dose was gradually increased to 10mg \u2013 and she was determined to make it work. \u2018I followed the instructions on how to inject myself to the letter; cut down on portion sizes; practised mindful eating \u2013 eating slowly and removing distractions; and I walked my dog for an hour a day,\u2019 she recalls.<\/p>\n

Initially she lost a few pounds but, she says, \u2018that was more due to my willpower than a lack of appetite. The drug clearly wasn\u2019t working as I still felt so hungry all the time.\u2019<\/p>\n

At mealtimes, she and Myles ate the same food, \u2018but he\u2019d feel full and stop before finishing his plate. I could easily have eaten mine and finished his, too. I started to wonder what was wrong with me.\u2019<\/p>\n

Despite this, Olivia has persisted with her weekly injections, hoping the effects would kick in.<\/p>\n

Yet two-and-a-half years later, her diabetes is still not under control \u2013 and she still weighs 18st, with a BMI of 40.2. She remains on the drug as it seems to have controlled her chronic thrush infection. \u2018I am so disappointed I haven\u2019t lost weight,\u2019 she says. \u2018I posted about it on social media, and from the response I got it\u2019s clear I\u2019m not the only one.\u2019<\/p>\n

Olivia is now on the waiting list for bariatric (weight-loss) surgery. While the vast majority of people taking GLP-1 drugs lose significant amounts of weight, a sizeable minority do not, something many of those on them may not realise.<\/p>\n

A 2025 study involving around 480 people attending an obesity clinic found that almost one in five \u2013 nearly 20 per cent \u2013 were classed as \u2018non-responders\u2019, meaning they lost less than 5 per cent of their body weight, reported the BMJ Open.<\/p>\n

The figure is higher than in drug trials, where around 5 per cent were found to be non-responders.<\/p>\n

\u2018Some people have a low sensitivity to GLP-1s, and just hammering that system with higher doses will not produce sufficient results,\u2019 says Dr Simon Cork, a senior lecturer in physiology at Anglia Ruskin University.<\/p>\n

Professor Giles Yeo, a molecular endocrinologist at the University of Cambridge, says that while trials show around 20 per cent of people don\u2019t lose weight on GLP-1s, there will be practical reasons for this, such as stopping taking the drug due to side-effects or they can\u2019t afford it.<\/p>\n

He puts the number who genuinely can\u2019t lose weight on the drugs at around 5 per cent. This may be largely down to genes.<\/p>\n

A study just published by the University of Copenhagen identified two gene variants linked to how much weight people lose on the weight-loss injections.<\/p>\n

Dr Cork adds that the underlying reason an individual develops obesity can also vary \u2013 this may in turn affect how they respond to the drugs. For instance, a GLP-1 drug wouldn\u2019t help with weight gain due to an underactive thyroid, as it is caused by a hormone imbalance.<\/p>\n

It\u2019s the same with polyendocrine metabolic ovarian syndrome (PMOS, previously called polycystic ovary syndrome) \u2013 which Olivia has \u2013 a common hormonal condition that affects how the ovaries work and the way the body processes energy and stores fat.<\/p>\n

Dr Cork adds that hundreds of genes can predispose someone to weight gain, each contributing a small but cumulative effect.<\/p>\n

A lack of response to medication is a widespread issue across many commonly prescribed drugs.<\/p>\n

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\"\u2018The <\/div>\n<\/p><\/div>\n

\u2018The effects of drugs are far more uncertain than we expected \u2019 Professor Barber tells Good Health<\/p>\n<\/div>\n

For instance, research suggests antidepressants, strong painkillers (e.g. codeine and tramadol) as well as blood thinners (e.g. warfarin and clopidogrel) do not work effectively for everyone.<\/p>\n

Indeed, as a 2015 study, published in Nature, found, the ten bestselling drugs in the US only worked in a quarter of patients \u2013 and half didn\u2019t work in 90 per cent of patients.<\/p>\n

These included the heartburn drug omeprazole, which helped only one in 25, and the statin rosuvastatin, which helped one in 20, as Nick Barber, a professor emeritus of pharmacy at University College London, points out in his new book, How To Take Drugs.<\/p>\n

\u2018The effects of drugs are far more uncertain than we expected \u2013 and because of that we need an approach to decide whether to take them, stay with them or stop them,\u2019 Professor Barber tells Good Health.<\/p>\n

And, increasingly, scientists are looking at the role of genetics in drug metabolism, known as pharmacogenetics, with some experts arguing genetic testing should be offered more widely to help doctors and pharmacists tailor treatment according to how an individual will respond to medications.<\/p>\n

\u2018Your genes can affect how your liver breaks down a medicine, for instance, and how your body responds to it,\u2019 explains Professor Amira Guirguis, chief scientist at the Royal Pharmaceutical Society. \u2018They can also determine whether a drug binds properly to its target in order to produce a response in the body.\u2019<\/p>\n

Indeed, as many as 89 per cent of patients aged 70 and above had been prescribed at least one drug affected by their genes over the previous two decades, according to a 2019 study published in the British Journal of Clinical Pharmacology. Even among those aged 50 to 59, the figure was 71 per cent.<\/p>\n

Professor Sir Munir Pirmohamed, NHS chair of pharmacogenetics at the University of Liverpool, says 99.9 per cent of the UK population have at least one gene variant that affects how a drug will work for them, and one in four people have four of these variants.<\/p>\n

The benefits of testing individuals for such variants were highlighted in the PREPARE trial, published in The Lancet in 2023, which found screening patients for 12 genes \u2013 and adjusting medications accordingly \u2013 reduced adverse drug reactions by 30 per cent.<\/p>\n

\u2018This type of screening could save the NHS some of the \u00a32.2 billion it spends each year treating adverse drug reactions,\u2019 says Professor Pirmohamed, who points to countries such as Spain, the Netherlands and US \u2018which are doing this already, where there is good evidence that it makes a difference to patient lives\u2019.<\/p>\n

He adds: \u2018And the list of drugs that require genetic testing will grow as evidence builds.\u2019<\/p>\n

The feasibility of introducing a nationwide NHS genetic testing service is currently being assessed in the PROGRESS trial, led by the North West Genomic Medicine Service Alliance. Patients in the study are offered a simple blood or saliva test to identify gene variants affecting drug response. The results so far are striking: 28 per cent of patients needed their prescription changed based on their genetic profile.<\/p>\n

A second phase is now under way, involving 1,350 patients across the UK. It uses a tool called ProgressRX, which converts genetic data into prescribing advice for GPs.<\/p>\n

Professor Pirmohamed says the long-term goal is to have everyone\u2019s genetic profile recorded and available through the NHS app, so doctors and pharmacists can tailor treatment. \u2018We want to move towards pre-emptive testing, so it\u2019s there in your GP records,\u2019 he adds.<\/p>\n

Professor Yeo believes that within 15 to 20 years genome sequencing at birth could become routine.<\/p>\n

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\"Dr <\/div>\n<\/p><\/div>\n

Dr Cork says that hundreds of genes can predispose someone to weight gain, each contributing a small but cumulative effect<\/p>\n<\/div>\n

Such genetic tests are in fact already available on the high street, including Bupa\u2019s My Genomic Test, \u00a3225, which analyses DNA responses to more than 100 common medicines, as well as Get Tested (\u00a3249.99, gettested.co.uk), which offers a DNA Pharmacogenetics check that covers 50 medicines. The Day Lewis chain offers it at its Stockwell branch in south London for \u00a3199, including a consultation.<\/p>\n

In the course of writing his book, Professor Barber underwent the test at Day Lewis, which identified 16 drugs he might not respond well to. \u2018One was the painkiller codeine. I lacked enough of an enzyme to break it down, so it wouldn\u2019t work for me,\u2019 he says.<\/p>\n

\u2018Another was flecainide. The test revealed I couldn\u2019t break the drug down, so it could quickly reach toxic levels in my body and should be avoided. In fact, I\u2019d been prescribed this drug in the past for an irregular heartbeat, but stopped after one tablet because I felt my heart racing.\u2019<\/p>\n

As well as genes, there are many reasons why medication may not work. These include not taking it as directed and interactions with other medications or foods. For example, grapefruit juice can hinder the effectiveness of cholesterol-lowering statins.<\/p>\n

Underlying liver or kidney disease can also affect drug effectiveness \u2013 both organs are involved in the breakdown and removal of medication from the body, so if they aren\u2019t working effectively then drugs can build up and potentially become toxic.<\/p>\n

Professor Barber adds: \u2018Your body size can also affect how your medication will work.<\/p>\n

\u2018If you are overweight or obese, some drugs may sit in fat cells and not circulate and work as intended. Meanwhile, if you are small, then the same dose that works for a big rugby player, for instance, may cause you more side-effects as there\u2019s a higher concentration in your blood.\u2019<\/p>\n

There is also emerging evidence that the gut microbiome \u2013 the community of bacteria and other microbes that play an important role in health \u2013 may also affect how drugs are broken down in the body.<\/p>\n

\u2018The microbiome can activate a drug, inactivate it or make it more toxic,\u2019 says Professor Barber.<\/p>\n

Indeed, a 2022 study in the journal Microbial Ecology illustrated just how powerful gut bacteria can be. It found the bacterium H.pylori \u2013 which an estimated two in five Brits has in their stomachs \u2013 could impair absorption and effectiveness of the drug levodopa used for Parkinson\u2019s disease, for example; and E.lenta (thought to be present in 80 per cent of people\u2019s gut) inactivated the drug digoxin, used to treat heart failure.<\/p>\n

\u2018Just as two people can follow the same recipe and get different results because they have different kitchens, our bodies can respond very differently to medicines,\u2019 explains Professor Guirguis.<\/p>\n

So what should you do if you don\u2019t think your medication is working?<\/p>\n

Professor Barber says with some drugs \u2013 such as those for pain or acid reflux \u2013 you should know within a few days of taking them, as you would get physical symptom relief. \u2018If they aren\u2019t having an effect, go back to your GP \u2013 they may try a higher dose or prescribe an alternative.\u2019<\/p>\n

For other drugs such as blood pressure pills or statins, you might not feel different. But \u2018in these cases, it is worth investing in a blood pressure monitor and having a blood test for cholesterol at least once a year. And with antidepressants you should feel an effect within four weeks \u2013 this is one area where pharmacogenetic testing would make it easier,\u2019 he adds.<\/p>\n

As for GLP-1s, if you haven\u2019t lost at least 5 per cent of your body weight after taking the full dose for three to six months, you\u2019ll probably need to change the treatment or look to other ways to lose weight, says Alex Miras, a consultant in endocrinology at Imperial College Healthcare NHS Trust in London.<\/p>\n

And if you are on long-term medication, your GP should offer you an annual medication review to check symptoms, side-effects and how well a drug is working.<\/p>\n

How To Take Drugs, by Professor Nick Barber (Bluebird, \u00a322) is out on Thursday.<\/span><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Olivia Hillary was over the moon when she was prescribed Mounjaro on the NHS to control her type 2 diabetes. While GLP-1 drugs such as Mounjaro are better known for weight loss, they were actually developed for type 2 diabetes and Olivia was desperate to improve her health. She had tried \u2018every diet going\u2019 since<\/p>\n","protected":false},"author":1,"featured_media":9764,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_bunyad_sub_title":"","footnotes":""},"categories":[520],"tags":[],"class_list":["post-9763","post","type-post","status-publish","format-standard","has-post-thumbnail","category-hot"],"_links":{"self":[{"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/posts\/9763","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9763"}],"version-history":[{"count":0,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/posts\/9763\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=\/wp\/v2\/media\/9764"}],"wp:attachment":[{"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9763"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9763"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.healthoptibody.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9763"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}