Of course. If you don't fulfill the expectations of your job... you get fired.
As SeisK mentioned, everything is circumstance dependent. Some groups will give you a lot of rope to get your speed up. In the current market, where a lot of groups are short staffed, they might give you a lot more rope or a lot less rope.
In any event, *if you're slow* you better make sure your reads are quality and you're well-liked.