Since 1985, Guy has worked as an activist, clinician, and director of programs providing services for injection drug users, sex workers, incarcerated persons and homeless people living with HIV. In the 1980s and 1990s he also worked as a hospice attendant, a special duty nurse at San Francisco General Hospital's inpatient HIV/AIDS Unit 5A (formerly 5B) and as a consultant for HIV care in prisons and jails across the USA.
After joining UCSF in 2004, Guy spent ten years providing training and technical assistance with the rollout of antiretroviral treatment in Eastern and Southern Africa, focusing primarily on the diagnosis and treatment of infants and children.
When not in Africa, Guy worked at UCSF’s HIV Clinic at San Francisco General Hospital, Ward 86, where he provided care coordination, triage & urgent care, conducted a monthly Reproductive Health Clinic for individuals and couples affected by HIV, and facilitated the clinic’s Opiate Prescribing & Pain Management Committee.
The 2018 release of the award-winning documentary "5B" about the first hospital ward dedicated to patients with HIV/AIDS (www.5Bfilm.com) led Guy and his husband Steve to travel extensively across the US and Europe. They returned to San Francisco at the same week the first case of COVID-19 was diagnosed in the City. During the first few months of the pandemic, Guy volunteered at the COVID Emergency Field Hospital that was set up at Southeast Health Center, and during the late Spring and Summer he self-deployed to San Quentin State Prison to assist in the efforts to contain the outbreak there.
In September of 2021, he returned to SFGH to assist the COVID-19 SF-DPH Occupational Health taskforce with case investigation and contact tracing. Currently, Guy divides his time between the COVID taskforce, the HIV-services at SF-DPH Health at Home, and the Pacific AIDS Education and Training Center.