Know all about 'golden blood,' the rarest blood type

The surface of blood cells is coated with up to 342 antigens whose combination determines a person's blood type.

In 1961, a new type, that lacked all 61 antigens in the Rh system, was discovered. It was named Rh-null. 43 people have had it, but currently there are only nine active donors, making it the world's most precious blood type (hence the name golden).

People with Rh-null blood can be universal donors but because of its rarity, it can get extremely difficult for them, should they need it.

Besides, donating the golden blood across borders isn't easy. The process is often hampered by bureaucracy. Some countries just don't allow it. Those who do, don't pay the donors for travel, forcing them to do it at their own expense.

There are no side-effects or health complications of having Rh-null blood type. Though such people can be mildly anemic, they can lead regular lives.

However, because of the rarity of their blood, they need to be extra careful. They can't be reckless with activities than can cause injuries and result in blood loss. They also need to be more mindful than others when travelling.

Though not as precious as golden blood, the Bombay blood type is also considered one of the rarest.

Found in less than 0.0004% of the world population, it was discovered in Mumbai in 1952. The presence of antigen H makes it different.

People with it can receive blood only from their own group but can donate to blood types within the ABO phenotype realm.