Fraud and misconduct in medical and scientific research harm patients by corrupting the evidence used for clinical care, public health guidance, regulation, and trust. Fabricated, falsified, misrepresented or selectively promoted evidence can distort practice long after concerns emerge or papers are retracted. Case studies involving stem cells, anaesthesia, bone disease, vaccines, and opioid marketing based on a brief New England Journal of Medicine letter, outlined in this article, show how false or misused evidence can expose patients to unsafe interventions, skew guidelines and systematic reviews, waste research funding, fuel vaccine hesitancy, and contribute to large-scale public health damage. Reducing these harms requires practical safeguards across the publication lifecycle: rigorous peer review, robust publication policies, verification of source data and references, trial registration and results posting, data sharing, adherence to the Committee on Publication Ethics (COPE) and Good Publication Practice (GPP) principles, AI-assisted integrity checks, and retraction monitoring. Protecting the integrity of science is essential to patient safety.