People who shouldn't donate blood are people that have certain medical conditions, use certain medicaitons or people who are using illegal drugs.
If you have any active infections like flu, colds, sore throat or you have heart disease, have had a stroke, have high blood pressure, have cancer, hemophilia, HIV/AIDS, Hepatitis B or C or if you take or use anticoagulants or chemotherapy drugs, injection drugs or have had sexual activity with someone that has a sexually transmitted infection or have had a recent tattoo or piercing within the past 6 months.
Also if you're over 70 or under 17 or you have a low body weight of less than 110 lbs you might not be able to donate blood, but it can depend on local regulations.
Also if you have any history of fainting or seizures during blood donation or you're pregnant or have active tuberculosis you should not donate blood.
Rh-null is the rarest blood type.
The blood type Rh-null is also known as "Golden Blood".
People that have Rh-null or Golden Blood types lack all the Rh antigens on their red blood cells which makes their blood compatible with any other blood type.
However people with Rh-null blood type can only receive blood transfusions from other people with Rh-null blood types.
Rh-null blood type is so rare of a blood type that it's also estimated that there are only 50 known people with Rh-null blood type donors worldwide.
There could be more but it's just an estimate.
Other three rarest blood types in the United States are AB-, B-, and AB+. AB- is the least common, followed by B-, then AB+
O negative blood is also a rare blood type, although it's not the absolute rarest blood type, is considered relatively rare, with about 7% of the US population having it.
The O negative blood type is highly valued because it can be transfused to anyone, making it crucial for emergency situations where a patient's blood type is unknown or in short supply.
O negative blood lacks both A and B antigens (in the ABO system) and the Rh antigen, meaning it can be transfused to anyone regardless of their blood type.
And because of it's universal compatibility, O negative blood is also frequently used in emergency situations, in which there is not time to determine a person's blood type.
O negative blood type is also in high demand because of it being so vital for emergencies and so blood banks always actively seek donations of O blood type donations to be able to maintain sufficient supplies.
And also because only about 7 percent of the population has O negative blood types it makes it valuable and sought after.