Tomorrow night, all being well, Julianne Moore will be an Oscar winner.

At long last. Nominated five times, she's lost out every time so far. The last time, in 2003, was particularly painful. Up for Best Actress for her role as the conflicted 1950s housewife in Todd Haynes' Far From Heaven, she lost out to Nicole Kidman for The Hours, a film Moore was also in and nominated for in the Supporting Actress category. Who did she lose to? Catherine Zeta-Jones in Chicago.

Having also been overlooked for her porn star in Boogie Nights and her unfaithful spouse in The End Of The Affair, the 54-year-old Moore must've thought she was destined to forever be an Oscar bridesmaid. "At the end of the day, everyone likes to be validated - blue ribbons, prizes, stars," she says, diplomatically. "We all like that stuff. But more important than that are the jobs. I feel grateful to continue to be able to work and to have things that I love to do."

Maybe this is what she'll keep telling herself tomorrow night if, when that golden envelope is opened, her name is not read out. Except that this time, Hollywood's most famous red-head is the red-hot favourite; the film Still Alice - which plays at the Glasgow Film Festival tonight and tomorrow - has already won her a Golden Globe, a Bafta and a Screen Actors Guild award. Factor in her Best Actress win at last year's Cannes Film Festival for her hysterical Hollywood harridan in Maps To The Stars, and it seems this is her year.

Such is the strength of Moore's career you could name a dozen movies that she was not even nominated for that would merit an Oscar. Think of Safe, playing a woman paralysed by allergies, her pill-popping trophy wife in Magnolia, or the incestuous mother in Savage Grace (with this year's nailed-on Best Actor winner Eddie Redmayne as her son). Raw, open, authentic, she regularly bares soul and body - most famously delivering a monologue naked from the waist down in Robert Altman's Short Cuts.

This being Moore, she modestly plays down the courage it takes to tackle these fraught women. "I think to be courageous you have to be afraid. For me, it feels very courageous when I go skiing because I'm very, very afraid to ski. It's dangerous! I feel very scared. But when I'm acting, I don't feel very scared." Even so, Still Alice - based on the book by Lisa Genova - is something else; Moore plays Dr Alice Howland, a linguistics professor who suffers from early-onset Alzheimer's, a rare but very real form of the disease.

Moore had no direct experience of Alzheimer's, but found it fascinating. "What's interesting is how many people have a deathly fear of this disease," she says, "and how little information there is about it. It's a big issue, Alzheimer's, and it's becoming more prevalent as people are living longer." Particularly intriguing was the fact the story is told subjectively, as Alice rapidly deteriorates across several months. "This is inside Alice's experience," she says.

It meant Moore had to undertake a wealth of research to try to understand what that might be like. "I spoke to everyone I could," she says, and she means it. She met researchers and clinicians at Mount Sinai Hospital in New York. She took a cognitive test for her memory, and later hooked up with the New York Alzheimer's Association, visiting support groups and talking to several women who were diagnosed with the condition. "I tried to meet everybody at every stage of the disease," she says.

Yet again, Still Alice offers an outpouring of emotion from Moore, who admits it's never easy to well-up on camera. "You have to connect to something in it. I'm not one of those actors who can sit around and make myself sad about something else. It doesn't work. But they have to be sad. It has to be in the story. It doesn't happen on a line. You don't know if it will happen at that moment. You just have to see where it will happen. It's like part of your skill set; it's part of what you're supposed to do."

While you might expect Moore to be constantly in bits playing such characters, she's so gosh-darn normal. "What did Flaubert say? 'Be ordinary in your life so that you can be violent and original in your work.' I believe that," she states. Admittedly, the fact she's a brand ambassador for cosmetic giant L'Oreal is hardly ordinary. But largely Moore has kept away from Hollywood temptation, living in New York with her filmmaker husband Bart Freundlich, and their two children, son Caleb, now 17, and daughter Liv, 12.

"They live a very regular life," Moore explains of her kids. "They both go to school in the city. I get up and make breakfast for them. My husband drives them to school. And we go to basketball games. Both my kids play a lot of basketball - my son's a really, really good player. We go to those games all the time. We have family vacations. We're very involved in their lives and they don't work! They don't have jobs. I don't think it's a good thing for kids to work."

It helps that she and her husband have found a way to balance work with parenthood. "We're fortunate that we have flexible schedules. I like that." Having already been married for nine years to actor John Gould Rubin, Moore met Freundlich on his 1997 film, Thanksgiving-set drama The Myth Of Fingerprints. They've worked together twice since - on the underrated World Traveller, Moore playing the disturbed Dulcie, and 2005's comedy Trust The Man, two years after they finally tied the knot.

Moore's own upbringing was not quite so stable. Born in the Fort Bragg army base in North Carolina, she spent her early years bouncing around the globe, from Paris to Panama, due her father military career. "It makes you adaptable," she says. "You are always trying to fit in." Her mother, Anne, a psychiatric social worker, came from Greenock - her own parents left for the United States when she was 10 and she would frequently tell Moore and her younger brother and sister that they weren't American. "She was very Scottish."

When Moore was seven-years-old, her father was applying for law schools, there was a ruling that he couldn't be married to a foreign national, and her mother had to give up her British citizenship. "When she came home, she cried. She was so upset," remembers Moore. In 2011, two years after her mother died, Moore claimed dual nationality - as an emotional nod to her mother. Even one of her children's books - she began writing in 2007, with the hit Freckleface Strawberry - was called My Mom Is A Foreigner, But Not To Me.

Dressed today in a silver, high-necked dress and heels, she exudes effortless elegance - far removed from her childhood, when she was "the kid who's too short, the kid who wears glasses, the kid who's not athletic". Things changed in her teens; attending the American High School in Frankfurt, it was a formative period. "It was the first time I saw machine guns at an airport. They'd check under your car for bombs. One of my friends identified a member of the Baader-Meinhof gang in a pizza place. That long before anyone in the United States felt affected by terrorism."

If there is to be an Oscar tomorrow, it'll have been a long old road for Moore after she began acting in high school: a theatre degree at Boston University, a spell on soap As The World Turns, playing dual roles as half-sisters, and even a potentially career-ending role with Madonna in the much-maligned Body Of Evidence. But by the mid-1990s, she'd worked with Robert Altman and Todd Haynes. Steven Spielberg picked her to battle dinosaurs in Jurassic Park sequel, The Lost World. And later, she took from Jodie Foster as Clarice Starling in Hannibal.

She'll be back in a blockbuster later this year, playing the silver-haired rebel President Alma Coin in the final Hunger Games outing - a film she pursued for the sake of her kids. "They don't care about movies, but this one they care about." She's also just wrapped Freeheld, a legal drama in which she plays a woman with terminal lung cancer. Another harrowing role, Moore wouldn't have it any other way. Is there anything she can't do? "I'm not much of a cook," she sighs. "I can just about assemble a dinner." Well, she can always order takeaway.

Still Alice screens at GFT tonight at 9pm and tomorrow at 3pm as part of the Glasgow Film Festival, www.glasgowfilm.org/festival. It goes on general release on March 6