The 'How to Get Away with Murder' star knows diabetes - which affects the body's ability to process insulin - runs in her family so has always followed a balanced diet and tried to exercise regularly in a bid to avoid the condition but she was stunned when a routine blood test in August 2016 flagged that her blood sugar levels were high.
She told People magazine: "I actually didn't even know what to do, I have to say. I felt like I didn't have a lot of resources. I consider myself to be a healthy eater, I exercise, I do it all."
Following her diagnosis, the 53-year-old actress has rededicated her time and energy to her health because she wants to "be around" for her eight-year-old daughter Genesis, who she has with husband Julius Tennon.
She said: "I want to be around for my daughter. I want to stay healthy for as long as I can for her."
Viola has teamed up with Merck on America's Diabetes Challenge to narrate the documentary 'A Touch of Sugar', and as soon as she heard about the project, she knew she had to get involved.
She said: "It hit home for me. It's something that's an ongoing conversation in my life. My two sisters have Type 2 Diabetes, my great aunt had Type 2 Diabetes. (She) lost both of her legs and was in a wheelchair for decades, up until she finally succumbed to the disease. As did my grandmother on my father's side."
And the 'Widows' star wanted to acknowledge the way being diagnosed with diabetes "shifted the lives" of her sisters, Dianne Davis-Wright and Deloris Grant, but they are doing all they can to stay healthy.
She said: "[Diabetes] has affected them in different ways, in terms of the symptoms they've had.
"But the thing that's even more important is that they're managing it. They have tackled it. They're not just watching it and sitting by."