Some people may argue that because they are going to feel something different, it is because their blood pressure was lowered right after donating the blood. But there is no way to tell.
Blood pressure may be affected or be lowered right after blood donation, but if it was, it could be just temporary.
In fact, if you have high blood pressure along with many other requirements, you will not be allowed to even donate blood in the first place.
So, the answer is no, it does not remove the danger.