Every year, tens of millions of antibiotic prescriptions are written in the UK for conditions they cannot treat. The damage this does to the human gut — quietly, cumulatively, across generations — is one of the most significant unacknowledged public health crises of our time. And the industry that profits most from it would rather you didn’t join the dots.

There is a number that should stop you in your tracks.

The total number of antibiotic-resistant infections in the UK in 2024 equates to an average of nearly 400 newly reported cases every single week. Deaths in people with a resistant infection rose from 2,041 in 2023 to 2,379 in 2024 — an increase of 338 people in a single year.

That figure gets reported. It generates headlines about antibiotic resistance, global superbugs, the post-antibiotic apocalypse. Health ministers make grave statements. Action plans are published. Targets are set, and mostly missed.

What doesn’t get reported — not with anything approaching the same urgency — is the other damage antibiotics are doing. Not to resistant bacteria. To you. To your gut. To the microbial ecosystem that governs your immune function, your metabolic health, your inflammatory response, your children’s risk of asthma and obesity and autoimmune disease.

That damage is quieter. It doesn’t present as a resistant bloodstream infection. It presents as a child who keeps getting chest infections. As an adult with IBS that appeared after a course of antibiotics a decade ago and never quite resolved. As a generation of people with chronic inflammatory conditions whose connection to antibiotic overuse in infancy has been documented in the literature and ignored in the clinic.

This is the antibiotic catastrophe nobody is counting. And it is happening at scale, right now, in a regulatory environment that has so far treated it as an acceptable cost of doing business.

What antibiotics actually do to your gut

Let’s start with the biology, because it is more disturbing than most people realise.

Your gut microbiome contains somewhere between 500 and 1,000 distinct bacterial species, distributed across 38 trillion individual organisms. This ecosystem took approximately four years of your early life to assemble — shaped by how you were born, whether you were breastfed, your early environment, your diet — and it will influence virtually every aspect of your health for the rest of your life.

Antibiotics are not surgical instruments. They are chemical blunt-force weapons. They do not distinguish between the pathogen they were prescribed to eliminate and the commensal organisms that constitute your gut ecosystem.

Broad-spectrum antibiotics can affect the abundances of 30% of the bacteria in the gut community, causing rapid and significant drops in taxonomic richness, diversity and evenness. A single course. Seven to ten days. Thirty percent of your gut ecology, disrupted.

For years, the reassurance offered by clinicians was that the microbiome recovers. Resilient ecosystem, temporary disruption, back to normal within weeks. The research is now telling a considerably different story.

On average, people who had not taken any antibiotics in the past eight years had about 350 unique bacterial species living in their gut, but those who had taken any antibiotics in that time frame had fewer. That finding comes from a landmark 2026 study published in Nature Medicine, which cross-referenced the gut microbiomes of nearly 15,000 Swedish adults with their individual antibiotic prescription records over eight years.

Each course of clindamycin taken in the year before sampling was associated with an average of 47 fewer species detected. Each course of fluoroquinolones was associated with 20 fewer species. Use of clindamycin, fluoroquinolones, and flucloxacillin one to four years and four to eight years before sampling was still significantly associated with reduced gut microbiome diversity.

Read that again. Antibiotics taken four to eight years ago are still measurably affecting the composition of your gut today. The analysis showed bacterial diversity recovered fastest in the first two years after antibiotic use, then more slowly thereafter. “It seems like you don’t recover completely,” said Tove Fall, the study’s senior author and a molecular epidemiologist at Uppsala University.

Researchers at UCL put it more starkly. “People have known that antibiotics decrease the diversity of microbes in the gut before it recovers, but the model we’ve developed suggests that the disturbance may transition the microbiome to a new composition, perhaps permanently,” said Dr Liam Shaw of UCL’s Genetics Institute. “If you picture the state of the microbiome as a ball resting in a valley, antibiotics can ‘kick’ the ball up and out of the valley into a different valley, where it may not be able to return to the first one.”

A new valley. A permanently altered ecosystem. From a single course of antibiotics.

The inappropriate prescribing problem

Here is where the systemic failure becomes impossible to ignore.

Inappropriate prescribing of antibiotics in primary care is estimated to be around 20% of antibiotic prescriptions in England — a level described by Parliament’s Public Accounts Committee as “too high” and a driver of antimicrobial resistance. Inappropriate includes prescribing antibiotics for viral infections they cannot treat, prescribing the wrong antibiotic, or using them for longer than necessary.

About 60% of antibiotic prescribing in primary care is for respiratory tract infections, a substantial proportion of which is deemed unnecessary, being given for viral or self-limiting RTIs.

Cold. Flu. Sore throat. Viral chest infection. Conditions for which antibiotics are pharmacologically useless — they cannot kill viruses — but for which they are routinely prescribed anyway. Sometimes because the patient demands them. More often because a ten-minute GP appointment under extraordinary operational pressure is not the environment in which nuanced antibiotic stewardship conversations reliably happen. Sometimes because prescribing is simply easier than not prescribing.

Drug-resistant infections increased by 13.1% between 2019 and 2024, with most of this increase seen in the last two years. This is the resistance story — the headline metric, the one that drives government policy and media coverage.

But behind every one of those prescriptions — appropriate and inappropriate alike — there is a gut microbiome being disrupted. A microbial ecosystem losing diversity. A person who, according to the latest evidence, will carry some portion of that disruption for years.

Between 2019 and 2024, while NHS primary care antibiotic use decreased slightly, private dispensing in community pharmacies more than doubled, resulting in an overall 10.7% increase in primary care antibiotic use. By 2024, 22% of antibiotics were dispensed through the private sector.

The NHS stewardship programmes are working — slowly, partially, against the tide. Meanwhile, the private prescribing market is expanding, subject to less systematic oversight, driven partly by the same patient demand dynamics and partly by commercial incentives that don’t exist in the NHS system. The net result: more antibiotics, not fewer.

The children: where the damage is most profound

The science of antibiotic damage to the gut is concerning in adults. In children, it is alarming.

The first years of life are the window during which the gut microbiome is assembled — the critical period when microbial colonisation shapes immune system development, metabolic programming, and inflammatory response for decades to come. The community of microorganisms gradually becomes more diverse with age, typically reaching stability at between two and four years. These first four years of life are critical for establishing a healthy microbial community.

Antibiotics prescribed during this window don’t just cause a temporary disruption to an established system. They interfere with the construction of that system during its most formative phase.

Early antibiotic exposure — the most commonly prescribed medication in young children and frequently overused — is associated with increased risk of childhood-onset diseases and neurodevelopmental conditions, with other studies finding links to a higher risk of obesity. The hypothesis is that these conditions may be occurring because of the way antibiotics disrupt the gut microbiome, which is still in development in infants.

Antibiotics in childhood have been linked with diseases including asthma, juvenile arthritis, type 1 diabetes, Crohn’s disease and mental illness, with the underlying mechanisms thought related to dysbiosis of the gut microbiome — so concluded a systematic review published in Gut Microbes by researchers at King’s College London.

Macrolide use in early life is associated with a long-lasting shift in microbiota composition and metabolism, including depletion of Actinobacteria, increase in Bacteroidetes and Proteobacteria, decrease in bile-salt hydrolase, and increase in macrolide resistance — microbiota characteristics previously associated with the risk of immunological and metabolic diseases, as well as obesity.

In a cohort study of 152,622 children, antibiotic use in infancy significantly increased the risk of childhood asthma in a dose-dependent manner. More courses, greater risk. The relationship is not subtle. It is dose-dependent, replicated, and documented across multiple populations.

These are not correlation artefacts. The mechanistic pathway is understood: antibiotics disrupt early-life microbial assembly, which disrupts the immune system calibration that occurs in the first years of life, which increases lifetime susceptibility to conditions characterised by immune dysregulation — asthma, allergies, inflammatory bowel disease, type 1 diabetes.

We are giving our children a drug that disrupts the biological process most responsible for training their immune systems, during the window when that training is most consequential, for conditions the drug cannot treat.

The multigenerational dimension nobody discusses

The story gets darker still when you extend it across generations.

There is now evidence that antibiotic-induced microbiome disruption is not confined to the individual who receives the prescription. Antibiotic use before, during or immediately after pregnancy is associated with an increased risk of childhood allergy, asthma, atopy and obesity in the child — suggesting that maternal antibiotic exposure alters the microbial environment passed from mother to infant.

The founding microbiome — the first colonisation of the infant gut, which occurs during vaginal birth and breastfeeding — is drawn substantially from the maternal microbiome. A mother whose gut diversity has been reduced by antibiotic courses over her lifetime passes a diminished microbial legacy to her child. That child’s immune system develops against a less diverse microbial backdrop. Their risk of inflammatory and metabolic disease is elevated accordingly.

This is not speculation. It is documented in the peer-reviewed literature and almost entirely absent from public health communication around antibiotic use.

We talk about antibiotic resistance as an intergenerational threat — the drugs we overuse today will be ineffective for our grandchildren. We do not talk, with anything like equivalent seriousness, about the intergenerational microbiome damage that antibiotic overuse is producing right now. Not because the evidence is weak. Because the story is harder to tell, harder to count, and inconvenient for systems that depend on antibiotics as the default clinical response.

The conflict of interest at the heart of the story

Here is what the probiotic industry does not want you to notice — and what, once you see it, is difficult to unsee.

The global probiotics market was valued at $76.59 billion in 2025 and is projected to reach $114.95 billion by 2030. Among the key demand drivers cited in industry analysis: “higher antibiotic use that impacts the gut microbiota.”

Read that with the attention it deserves. The probiotic industry — which presents itself as an ally of gut health, a counterforce to the damage being done to human microbiomes — explicitly identifies antibiotic prescribing as a driver of its own commercial growth.

Every inappropriate antibiotic prescription is, from the probiotic industry’s perspective, a potential customer. Every child whose gut is disrupted by a course of amoxicillin for a viral ear infection is a candidate for a probiotic yoghurt drink, a capsule, a gummy, a personalised microbiome test, a subscription supplement programme.

The industry has every financial incentive to ensure that antibiotics continue to be overprescribed. It has no financial incentive to campaign for the diagnostic infrastructure, the prescribing reform, or the public health communication that would reduce inappropriate antibiotic use. It has every incentive to be the solution to the problem. It has no incentive to prevent the problem from occurring.

Industry reports note that healthcare professionals are increasingly recommending probiotics as adjuncts to antibiotic therapy and pediatric nutrition, strengthening demand in clinical and pharmacy-led channels. The GP who prescribes an antibiotic often recommends a probiotic in the same breath. The pharmacist who dispenses the antibiotic sells the probiotic from the same counter. The system is vertically integrated in its dysfunction.

And as we have established in previous articles in this series, the probiotic prescribed or recommended in this context — the Activia, the own-label capsule, the acidophilus tablet from the pharmacy shelf — is, in most cases, doing very little to restore what the antibiotic has disrupted. The organisms are not viable. They don’t colonise. The ecosystem that has been disrupted by a broad-spectrum antibiotic is not restored by a single strain of Lactobacillus acidophilus in a yoghurt drink.

The probiotic industry benefits from antibiotic damage. It cannot fix antibiotic damage. It profits from the gap between those two facts.

What the resistome adds to the picture

There is one further dimension of antibiotic damage that receives almost no attention in consumer-facing health communication.

Every course of antibiotics doesn’t just kill susceptible bacteria. It selects for resistant ones — organisms carrying antibiotic resistance genes that survive the treatment and repopulate the gut in the aftermath. Most healthy adult microbiomes return to pre-treatment species richness after approximately two months, but with an altered taxonomy, altered metabolic output, and an increased antibiotic resistance burden.

Your gut becomes a reservoir of resistance genes. Not just immediately after treatment — persistently, for months and years. Those resistance genes can be transferred horizontally to other bacteria, including pathogenic ones. The resistance you carry in your gut can, under the right conditions, become the resistance that makes a future infection untreatable.

The antibiotic resistance crisis is usually framed as an ecological problem — we are selecting for resistant organisms in populations and environments. It is equally a personal biology problem. Each prescription contributes not only to population-level resistance but to the individual’s own internal resistance reservoir.

People living in the most deprived communities had a 47.2% higher rate of resistant bacteraemia compared to those in the least deprived areas — an increase from a 29% difference in 2019, representing a widening of health inequality directly linked to antibiotic dynamics.

The communities that have historically received the most antibiotic prescriptions — poorer communities, with less access to diagnostic precision and more exposure to conditions that generate antibiotic demand — are now paying a double penalty: greater resistance burden, and, by implication, greater microbiome damage and its downstream health consequences.

The diagnostic infrastructure that could fix this — and doesn’t exist

The single most tractable intervention in this entire picture is rapid point-of-care diagnostics — tests that can determine, at the time of the GP appointment, whether an infection is viral or bacterial. If a GP can confirm within minutes that a patient’s respiratory infection is viral, the case for prescribing antibiotics disappears.

The government’s 2019 to 2024 national action plan had a target to be able, by 2024, to report on the percentage of prescriptions supported by a diagnostic test or decision support tool. This target was not achieved due to continuing limitations with data and a lack of central recording infrastructure.

The target was missed. The infrastructure was not built. The inappropriate prescribing continued.

This is not a technological problem. Rapid CRP tests, lateral flow tests for streptococcal infection, and point-of-care diagnostics capable of distinguishing viral from bacterial respiratory infection exist. They are used in some GP settings and not others. They are not systematically available, not systematically funded, and not systematically required.

The government spent £567 million on AMR programmes between 2020 and 2024. The diagnostic infrastructure that would most directly reduce inappropriate prescribing — and therefore most directly protect the gut microbiomes of the 56 million people in England — remains patchy, underfunded, and non-mandatory.

What you can do, and what the system should do

The honest individual-level answer is both simple and limited. If you are offered an antibiotic for a viral infection — a cold, flu, or viral sore throat — and you understand that it will do nothing to treat that infection while doing measurable, potentially lasting damage to your gut, you can decline it. You can ask the question. You can request confirmation that your infection is bacterial before agreeing to treatment.

Many people won’t. Many can’t — the clinical encounter doesn’t create the space for it, the information isn’t available in accessible form, and the power dynamics of the consulting room are not configured for patients who want to interrogate the prescription they’re being offered.

The systemic answer is more demanding. Mandatory point-of-care diagnostics before antibiotic prescribing for respiratory infections. Funding for the infrastructure that makes this possible. Public health communication that addresses not only antibiotic resistance — the story the system has prioritised — but microbiome damage: the story it has not.

And for the probiotic industry: an honest reckoning with its structural dependence on the problem it claims to solve. If the gut health movement were genuinely committed to protecting human microbiomes, it would be the loudest voice in the room demanding diagnostic reform and prescribing restraint. It is not. The silence is, in its way, diagnostic.

The number that should haunt us

Return, at the end, to where we started.

Almost 400 antibiotic-resistant infections reported every week in the UK in 2024. Nearly 2,400 deaths.

Behind each of those statistics is an antibiotic’s trajectory through a human body — killing a pathogen, perhaps, or perhaps not, while leaving behind an altered gut ecosystem, a reduced microbial diversity, a resistance gene reservoir, and — in children especially — a permanently changed immunological landscape.

We have been counting the wrong thing. Resistance is the catastrophe that’s visible, that fits into a news story, that generates political action. The microbiome damage is diffuse, cumulative, expressed across decades in conditions — asthma, inflammatory bowel disease, obesity, autoimmune disease — whose connection to antibiotic overuse is documented in the literature and invisible in the policy response.

The antibiotics were often necessary. Often they were not. In neither case was the damage to the gut counted, communicated, or weighed against the prescription’s benefit.

It is time to start counting.

References

1. Baldanzi et al. (2026). “Antibiotic use and gut microbiome composition links from individual-level prescription data of 14,979 individuals.” Nature Medicine

2. UKHSA ESPAUR Report 2024/2025. English Surveillance Programme for Antimicrobial Utilisation and Resistance. gov.uk

3. Shaw et al. (2019). “How antibiotics change human microbiome diversity long-term.” The ISME Journal, UCL

4. McDonnell et al. (2021). “Association between antibiotics and gut microbiome dysbiosis in children: systematic review and meta-analysis.” Gut Microbes, King’s College London

5. UK Parliament Public Accounts Committee (2025). “Antimicrobial resistance: addressing the risks.”

6. Dethlefsen & Relman (2011). “Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation.” PNAS

Image source: Karola G

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