The Royal College of Physicians of Edinburgh (RCPE) believes official recognition should be given to the man they feel has been 'airbrushed' from history.
They say Macleod's work, for which he received the 1923 Nobel Prize, is often forgotten as co-discoverers Frederick Banting and Charles Best actively sought to blacken the Scot's reputation.
Professor Brian Frier, at the RCPE, said: "The discovery of insulin is frequently and inaccurately attributed to Banting and Best, and for decades Macleod was effectively airbrushed out of medical history. John Macleod directed and informed the research which led to the discovery of insulin."
In the UK, almost four million people are prescribed insulin to treat type-1 diabetes. Before its discovery, the condition was considered to be 'rapidly fatal'.