I lost 2 games in a row due to not noticing that queen impatience is about to reach 12 points. Both times I had some completed but not delivered orders and could easily avoid defeat if noticed that I'm about to lose.
When queen impatience level reaches 11 points, the game displays warning notification, similar to "Food level low".
When impatience reaches, say, 11.95, the game shows "Queen impatience critical" notification and maybe pauses the game.
I agree that you can sometimes have games without noticing the severity. I think it's something that happens less as you play more but it was definitely a thing for me when I was getting used to the game. I'd like to suggest that the bar has a gradient from dark red (low Impatience) to bright red (high). Perhaps at ~75% onwards it also has a slow pulse which increases to a faster pulse as it gets higher. Nothing too distracting, but enough to notice it. Maybe just a 'spark' at the end of the bar which pulses. Or maybe the skull graphic starts glowing. Whatever it is, it should have a toggle in options for those who don't want the 'visual noise' of it trying to get their attention.