"You go, 'I don't want to look at that face anymore,' and I understand that, absolutely," the actress, 64, tells the British morning show GMTV.
And she refuses to judge women who seek out cosmetic treatments to make themselves look younger. "I think people should be allowed to do whatever they want to make themselves feel happy," Mirren says.
Mirren is famously considered that rarest of celebrities – a woman comfortable in her 60-something skin – as evidenced by the 2008 photos of her sporting a red bikini on vacation.
But that confidence was tested recently when she had to undergo a thorough examination of her body by the Madame Tussauds waxworks museum.
"To be measured by calipers, every inch of you, it's a bit intimidating," she told GMTV. "Every inch of you gets measured!"
Mirren got a sneak peek at the resulting wax figurine, which will be unveiled in April. "It was absolutely like having yourself next to yourself," she says. "It was very weird."
Still unclear: Whether her doppelgänger also has the small tattoo that Mirren now so despises.