Guidelines state that men should not drink more than 21 units of alcohol a week, and women 14 units. The study, published in the journal BMJ Open, analysed the GP records of nearly 28,000 people in the borough, reports The Guardian.
An alarming number of over-65s are drinking alcohol at unsafe levels, according to health experts who have carried out a study which found one in five are drinking unhealthy amounts.
Academics at the institute of psychiatry, psychology and neuroscience at King's College London said the baby boomer generation, of people born between 1946 and 1964, represents an ever increasing population of older people drinking at dangerous levels.
Analysis of the health records of people living in the London borough of Lambeth found that heavier drinkers were more likely to be male, wealthier and better educated. Less than half (46%) of people in the study were men, but they comprised 60% of the drinkers and 65% of those drinking at unsafe levels.
The study found drinkers were more likely to be white British or Irish, while people from Caribbean, African or Asian backgrounds were less likely to drink.
The median alcohol consumption was six units a week for the over-65s who reported drinking. In the top 5% of alcohol drinkers, men reported consuming more than 49 units a week and women more than 23 units.
Dr Tony Rao, the lead author, said: "As the baby boomer generation become seniors, they represent an ever-increasing population of older people drinking at levels that pose a risk to their health."
Dr Mark Ashworth, from the division of health and social care research at King's College London, said: "This research highlights that as GPs we need be more aware of the risk of older people, especially men, drinking excessively."