We study the speed with which physicians respond to changes in treatment guidelines, and estimate its effects on patient outcomes. We exploit unexpected information on the potentially adverse effects of drug-eluting stents (DES). Applying detailed micro-data on all percutaneous coronary interventions (PCI) performed in Swedish hospitals between 2002 and 2011, we measure physicians' adaptability as the rate with which individual cardiologists responded to new safety information regarding the use of DES. We find substantial variation across providers in their responses to information, that negative information generates more heterogeneous responses than positive information, and that more conservative adapters appear to perform better over a range of patient outcomes. These findings cannot be attributed to patient selection across cardiologist types.