If you're concerned about injury, you may have read up on how to create and use a tourniquet. However, you should also know that a tourniquet is not generally advisable to use unless direct pressure has already failed. If you are injured severely, it's important that you call 911 or go to emergency care or urgent care directly. A tourniquet should only be used if the bleeding is severe and cannot be stopped with direct pressure—it should not be used as the first course of action.
1. You Usually Don't Have the Right Materials On Hand
A tourniquet needs to be a thin, tight material that will not give at all. Often, these materials just aren't available. A strip of cloth usually will not work, despite what is shown in movies, because it will either tear or be too loose. The time wasted trying to find an appropriate tourniquet material is often best used applying direct pressure. If you do seem to need a tourniquet, it's best to have someone continue applying pressure while you look for one.
2. You Will Cut Off Blood Flow Completely
A tourniquet only works if it can cut off blood flow to the area completely. And this is very dangerous for the surrounding tissue. This is why a tourniquet is considered a last recourse. A person may lose a limb to a tourniquet. If the person is bleeding out, naturally the tourniquet is worth the risk. However, if the tourniquet is not necessary, a person may end up losing a limb or having damage to the limb for no reason.
3. You May Cause Further Damage
If the person in question has broken bones or other injuries, applying a tight tourniquet could cause unnecessary damage. It is often impossible for even trained professionals to tell whether there are internal injuries without equipment, so you may not realize that there is a broken bone or stretched tendon.
4. You Probably Don't Need To
By far the most compelling reason not to use a tourniquet is because you likely won't need to. Almost every bleeding injury can be stopped with direct pressure. The only situation in which a tourniquet is usually needed is when an artery is opened. This is very visible because blood will come out in fast gushes and spurts.
As noted, what you should try first in the case of bleeding is to apply direct pressure to the wound. Most wounds will stop bleeding with direct pressure. At the same time, someone should call 911 if the bleeding is severe. If the bleeding cannot be stopped and emergency services are not yet there, then and only then should a tourniquet be attempted.