Alzheimer's disease is the leading cause of dementia. However, neither Alzheimer’s disease nor Alzheimer’s dementia are an inevitable consequence of aging. This review provides an overview of the issues involved in a diagnosis of Alzheimer’s disease before an individual meets the criteria for Alzheimer’s dementia. It examines how Alzheimer’s disease diagnosis rates can be improved, the implications of an early diagnosis for the individual, carer and society, and the importance of risk reduction to prevent or delay progression. Although no disease-modifying agents capable of reversing the initial pathological changes are currently available, it may be possible to prevent or delay the development of dementia in a proportion of the population by modifying exposure to common risk factors. In other individuals, diagnosing the disease or risk of disease early is still valuable so that the individual and their carers have time to make choices and plan for the future, and to allow access to treatments that can help manage symptoms. Primary healthcare professionals play a pivotal role in recognising individuals at risk, recommending lifestyle changes in mid-adult life that can prevent or slow down the disease, and in timely diagnosis. Early intervention is the optimal strategy, because the patient’s level of function is preserved for longer.