The Cruel Intentions actor said doctors assumed her symptoms were psychological and would not give her “any real neurological tests”.
Blair, 50, received her diagnosis in 2018 after many years of illness. She first began experiencing fatigue, pain and mood swings when she was a child.
Speaking to BBC 100 Women, the actor said: “[The doctors] would say, ‘OK, what kind of trauma have you had?’ ‘We do think this is psychosomatic.’ But without any real neurological tests.”
Once she was diagnosed in 2018, Blair said she felt “unburdened”, but also felt “a little bit of panic, like how will I have the energy to ever even deal with this?”
“I have been down that road for so many years without a diagnosis that I did feel kind of hopeless still, but I was hoping that the diagnosis of MS would give me so many more options,” she continued.
Blair was named as one of 100 inspiring and influential women around the world on the BBC 100 Women list.
She frequently speaks out about living with MS, a lifelong condition that can affect the brain and spinal cord and causes a wide range of symptoms. It can sometimes cause serious disability.
Blair is known for her Instagram posts, in which she documents her symptoms and experiences with the condition.
In March, she shared a message of “strength” to mark MS Awareness Month alongside a video of herself over the last few years.
“March is #MSAwareness month,” she wrote in the caption. “May we all find the strength to persevere.”
Previously, Blair recalled the moment she knew was sick when her leg gave out while she was walking in a Christian Siriano fashion show in February 2018.
It was at that moment that she realised the symptoms were not psychosomatic, because she was happy to be walking in the show. A few months later, she told Variety, her hands “basically stopped working”.
Others who made it on this year’s list include Billie Eilish, Ukraine’s first lady Olena Zelenska, Priyanka Chopra, and Iranian climber Elnaz Rekabi.