What is a blood type and how does it affect my health?
What is a blood type?
Your blood type is a way that we classify blood. There are 4 types: A, B, AB, and O. The blood types are further broken down into positive or negative. We know the kind of blood you have based on whether or not your red blood cells have certain markers (like a flag) on their surface. There are four major groups: A, B, AB, and O. These major groups are then further broken down based on whether or not they have another marker called Rh factor. If the marker is present, your blood is classified as Rh POSITIVE. If it is not, your blood is classified as Rh NEGATIVE.
The main importance for this in medicine is helping to determine what blood would be safe to transfuse into you in an emergency. If you transfuse blood that has groups that your body is not used to it could trigger a lethal immune system reaction in which your body attacks the transfused blood.
Will knowing my blood type help me get a transfusion faster in emergency circumstances?
Not in general. In the United States, in addition to the basic blood type testing, they will also crossmatch your blood in order to more fully establish that certain blood is safe to give you.
In an absolute emergency - for example in a military field hospital where you are in imminent danger of bleeding out - they may skip this crossmatching and give you O negative blood that every body type can accept.
Does my blood type affect what foods I should eat?
Probably not. Although there are some books and websites that tell you to eat based on your blood type, we are not aware of any current scientific evidence that shows that it matters.
In some studies, for example, there was evidence that people who ate healthy foods and had blood type A had improved health, but so did all the other blood types in the study.
Overall the most reasonable advice is probably to just eat healthy generally, including avoiding excess empty carbohydrates like sugars.