Professor Gruer graduated from Edinburgh in 1975 with first-class honours in Medical Science.
He spent seven years practising clinical medicine and microbiology in the UK and France.
Professor Gruer then trained in public health in Glasgow, becoming a consultant in public health medicine with Greater Glasgow Health Board in 1989.
He led responses to HIV infection and drug misuse in Glasgow, setting up, managing and evaluating innovative services.
These included needle exchanges, the first supervised methadone programme in the UK, and dedicated clinical services for gay men, prostitutes and the homeless.
From 1996 to 2006 he was a member of the UK Advisory Council on the Misuse of Drugs, authoring an important report on the children of problem drug users.
In 2003 he became the first Director of Public Health Science, with NHS Health Scotland, the national health improvement agency.
He wrote two influential reports on tobacco control, leading to the highly successful ban on smoking in public places and other legislative changes.
Through his research and advice, he has influenced Scottish Government policy on alcohol, obesity, ethnicity and health, and socio-economic health inequalities.