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.