Familial hypercholesterolaemia (FH) is a common monogenetic condition that causes high levels of cholesterol in the blood, resulting in an increased risk of heart disease at an early age. FH affects around one in every 270 people. That means that in England around 160,000 adults and 40,000 children under 18 years are likely to have FH, though only around 3,000 have been diagnosed by DNA testing. This article discusses the new implementation guide, which is designed to improve the identification and treatment of people with FH.