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The Blood Type You’ve Probably Never Heard Of

Bombay Blood: Affecting just 4 million individuals globally, chances are you'll be learning something new today about the substance that unites us all...

LTT - Laboratory and Pathology Training | Brisbane, Melbourne, Perth & Sydney
August 2, 2018

If you know anything about blood, you might know that it is labelled with letters: A, B, AB and O according to which antigens are present on red blood cells, which react with our plasma. Blood type A cells display A ‘sugars’ (antigens) and B antibodies, B display B sugars and A antibodies, AB display both A and B sugars and no antibodies (hence are universal receivers) and O present neither of these sugars but both A and B antibodies.

You may also know another element of labelling blood: the presence or absence of an Rh Factor. Within these letter types an Rh factor may be inherited—or not.  In the case it is present in the blood, the person is noted as ‘Rh positive’, and if it is absent, ‘Rh negative’.

Putting these elements of blood type together, you might conclude that there are eight blood types in total. However, there are actually over 300 other rare blood types, one of which is the HH blood type. You see, to produce A and B sugar, the H precursor sugar is needed. The blood group O also expresses this sugar. HH blooded individuals do not produce this H sugar so have neither A or B sugars, and only have the H antibody. This means that those with the HH blood type are unable to receive blood from those with any other blood type without their antibodies attacking them, but are able to donate to all blood types (unless there is incompatibility in another blood factor such as Rh).

The incidence of the HH blood type is very low, and most commonly found in areas where there has been inbreeding within the population, also known as consanguinity. The first recorded case was found in Bombay, India (now Mumbai) in 1952, leading to the name ‘Bombay Blood’ given to the HH type. In India, approximately one in 17,600 people have Bombay Blood, and globally, it is estimated that there are about 4 million individuals with this blood type. This is likely because there are more Indian marriages where individuals are closely related to protect class and wealth status. Detection of Bombay Blood can be difficult without thorough testing, as it can appear similar to O type blood.

As you can imagine, Bombay Blood can make for make for some serious complications when individuals requiring it need surgery or are in medically dire situations. Most blood centres do not have Bombay Blood readily available, so if a transfusion is needed other countries may potentially need to be contacted for stores, or frozen stores accessed (as blood otherwise has a shelf life of around 35 days typically).

If you happen to be one of the 0.0004% of the human population with Bombay Blood, be sure to donate blood regularly– you’re one of the few who can save other people with HH Blood’s lives. In the more likely case that you don’t, however, hopefully you’ve learnt something new, and can perhaps pull this knowledge out in class!


If you have a fascination for blood, chemicals or anything in between, LTT offers a range of courses to satiate your curiosity and give you an edge ahead in a rapidly growing industry. Check out for more information and to get in touch!