You used to see a doctor. Now you go online.

Want to track your blood sugar? Your heart rate? Your sleep? You can.

Need to focus? Want to lose weight? Build muscle? Get pregnant? Advice is just a click away.

With long waits for treatment and fewer face‑to‑face GP appointments, influencers have stepped into the breach. From doctors promoting untested therapies to celebrities selling solutions, these self-styled experts radiate wellness and guarantee results.

Exploring the transformation of a healthcare system driven by online trends, Dr Deborah Cohen reveals the truth behind Ozempic influencers, AI-powered diagnoses, ‘preventative’ screening and Instagram’s favourite wearable tech.

Bad Influence is about the commodification of health in an age of anxiety and why we can no longer distinguish medicine from marketing.

Praise

‘Your definitive guide to separating medical facts from online fiction.’
Adam Kay, author of This is Going to Hurt

‘This superb book is an essential guide to the wild world of internet health.’
Chris van Tulleken, author of Ultra-Processed People

‘In a world where online medical opinions are fast and often dodgy, this is the perfect antidote.’
Prof. Kevin Fong

‘This fascinating and simultaneously terrifying dive into 21st century healthcare should be mandatory reading in 2026. Picking apart the fact from fiction and carefully delineating how our social media use is leading us into dark corners, you will read this book and become instantly better informed, self-aware and outraged’
Stylist, Best Non-fiction Books to read in 2026

‘Deb’s deeply reported, compelling analysis lays bare how social-media influencers, apps, algorithms and the rest of the digital ecosystem are transforming our health, for better or — often — for worse.’
Nature magazine

‘The first serious attempt to navigate a new wild west in which universal healthcare is being supplanted by the privatised apothecaries of Doctor Facebook and Professor Instagram… Cohen acts as navigator and envoy for a public understandably befogged by the untamed world of online quackery.’
The New World

‘Bad Influence is a fascinating and richly researched book, and an excellent guide for anyone who finds himself regularly googling their symptoms.’
The Economist