Hematologist
CION Cancer Clinics
Rare blood groups and the Bombay blood group | CION Cancer Clinics
The Bombay blood group is a rare inherited type where red cells lack the A, B and H markers. A quick test often labels it O, yet ordinary O blood can cause a serious reaction. Only Bombay group blood is safe to give. It causes no illness. It matters when you need blood, before surgery and in pregnancy, so knowing it early and recording it protects you. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What is the Bombay blood group?
- Why can a Bombay group person not take O blood?
- How is the Bombay group picked up in the lab?
- What should you do if you or a family member has it?
- What do the words on a blood group report mean?
- What do families get wrong about rare blood groups?
- Which other rare blood situations should you know about?
- Common questions about the Bombay blood group
The short answer
What is the Bombay blood group?
The Bombay blood group is a very rare type where your red cells carry none of the A, B or H markers that almost everyone else has. It matters because you can only safely receive blood from another person with the same Bombay type, not from an ordinary O group donor.
Why it has that name
It was first described by doctors in Bombay, now Mumbai, in the early 1950s. It is found in people all over the world, but it is seen more often in India than in most other countries.
What it means for your daily life
Nothing changes in your day-to-day health. The Bombay group is not a disease. It only becomes important on the day you need a transfusion, during pregnancy, or before planned surgery.
This page explains the blood group. It cannot confirm your own result. Only a blood bank test on your own sample can do that.Why it is different
Why can a Bombay group person not take O blood?
O group is often called the universal donor. For a Bombay group person it is not safe, and the reason sits in the plasma, the liquid part of the blood.
What a quick test shows
A basic grouping test looks for A and B markers on the red cells. A Bombay group person has neither, so the first result often reads as O group.
What your plasma carries
Your plasma makes strong antibodies, the body's defence proteins, against A, B and also H. Ordinary O cells are rich in H, so these antibodies attack them.
If the wrong blood is given
- The donated cells can be destroyed quickly
- This can cause a serious transfusion reaction
Who can give blood to you
Only another Bombay group donor. Brothers and sisters are the most likely people in a family to share it, so they are usually tested first.
Who you can give blood to
Your red cells carry no A, B or H markers, so in principle they suit many people. In practice, blood banks keep Bombay units for Bombay patients, because so few exist.
Not sure whether this applies to you?
Ask an oncologistIn the blood bank
How is the Bombay group picked up in the lab?
Cell grouping
The lab mixes your red cells with test liquids that look for A and B. With no reaction to either, the cells look like ordinary O group at this stage.
Plasma grouping
Next your plasma is mixed with known A, B and O cells. A true O group person's plasma leaves O cells alone. Bombay plasma reacts strongly with the O cells too, and that mismatch is the warning sign.
Confirming tests
The blood bank then tests for the H marker on your cells and anti-H in your plasma. Some samples are sent to a reference laboratory for confirmation.
Recording and a card
Once confirmed, the result should go on your hospital records, and you should be given a card to carry. Ask for this if it is not offered.
Planning ahead
What should you do if you or a family member has it?
Tell every doctor, every time. The most useful thing you can do is make sure the blood group is known before anyone needs to order blood. In an emergency, finding a matching unit can take time, and the search starts faster when the team already knows.
Before planned surgery
Tell the surgeon and the blood bank at the first visit, not the night before. Ask whether they will arrange Bombay units in advance.
During pregnancy
Tell your obstetrician at booking. The team will plan how to arrange blood in case of heavy bleeding at delivery.
Testing the family
The type is inherited from both parents. Brothers and sisters are the likeliest match, and cousins sometimes too. Testing them does not harm them, and a relative who turns out to be Bombay group can choose to join a rare donor list.
Never stop or refuse a transfusion on your own because of this. Talk to the treating team, who will arrange the right blood.Leave a number, we will call you
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On your report
What do the words on a blood group report mean?
- Oh or Bombay phenotype
- The short way a report writes the Bombay group. Phenotype means the type your blood shows on testing.
- H antigen
- A marker on the surface of red cells. It is the base on which A and B markers are built. Bombay group cells have none.
- Anti-H
- An antibody against the H marker. It is the reason ordinary O blood does not suit a Bombay group person.
- Para-Bombay
- A closely related rare type where a small trace of the marker is present. It also needs expert blood bank advice.
- Forward and reverse grouping
- The two halves of a group test: one checks the cells, the other checks the plasma. When they disagree, the lab investigates further.
- Rare donor registry
- A list of people with rare blood types who have agreed to be contacted when a patient needs their blood.
Commonly believed
What do families get wrong about rare blood groups?
"My card says O positive, so I cannot be Bombay group."
A quick cell-only test often labels a Bombay group person as O. Only a full group test, which also checks the plasma, reliably shows the difference.
"A rare blood group means something is wrong with my health."
It is simply an inherited type, like eye colour. It causes no illness. It only matters when you need blood or during pregnancy.
"In an emergency they will just give O negative."
That works for most people, but not for a Bombay group person. This is exactly why the group must be known and written on your records before an emergency happens.
"If I donate my rare blood, I will have none left for myself."
Your body replaces what you give. Your donor team will tell you whether donating suits you.
Beyond Bombay
Which other rare blood situations should you know about?
Bombay is the rare group most people in India have heard of, but it is not the only one. Some situations make finding matched blood harder, even when the main group is common.
Rh negative groups
Rh negative blood is far less common in India than in many other countries. It can be harder to find quickly in a smaller town.
People who have had many transfusions
People with thalassaemia, sickle cell disease or blood cancers often receive blood again and again. Over time, some make antibodies against minor markers on donor cells. Their blood then needs a closer match, which can take longer to find.
What this page cannot tell you
It cannot tell you your group, your antibodies, or how quickly blood can be found for you. Those depend on your own tests and on local stocks. If you are being treated for a blood disorder or blood cancer, CION's haematology team can review your reports, flag a rare group or antibody early, and help coordinate with blood banks that hold rare units.
Questions we are asked
Common questions about the Bombay blood group
How do I know if I have the Bombay blood group?
You only know through a full blood group test done by a blood bank, which checks both your cells and your plasma. If an earlier report said O group but a blood bank later found a mismatch, ask them directly whether the Bombay group has been tested for.
Can a Bombay group person receive O negative blood?
No. O negative cells still carry the H marker, and a Bombay group person's plasma attacks it. That can cause a serious reaction. Only Bombay group blood is safe. If you have this group, make sure every hospital you visit knows it before any blood is ordered.
Is the Bombay blood group dangerous for my health?
No. It does not cause any illness, weakness or symptom, and it does not shorten life. The only risk is receiving the wrong blood. Knowing your group, telling your doctors and carrying a card is what removes that risk in practice.
Will my children have the Bombay group too?
Not always. A child usually has it only when the gene comes from both parents. Your children will carry the gene, even if their own group is ordinary. If your partner is from the same family or community, testing the children is worth discussing with a doctor.
Where does a hospital find Bombay blood in an emergency?
Blood banks contact each other, state blood transfusion services and rare donor lists run by voluntary groups and larger blood banks. Relatives who are tested and found to match are often the quickest source. The search goes faster when the group is already on record.
Should a Bombay group person donate blood?
If you are healthy and meet the usual donor rules, donating is one of the most useful things you can do. Many blood banks will note you as a rare donor and call only when a patient needs your type.
What is the difference between Bombay and para-Bombay?
Both lack the usual markers on the red cells. In para-Bombay a faint trace of the H marker may be present or found elsewhere in the body. Both types need specialist blood bank advice before any transfusion, so the report should name exactly which one you have.
I am pregnant and have the Bombay group. What should I ask?
Ask your obstetrician whether the hospital's blood bank knows, and how they will arrange matching blood if there is heavy bleeding at delivery. Ask whether your siblings should be tested as possible donors. Plan early in the pregnancy rather than in the final weeks.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- NHS — Blood groups
- National Heart, Lung, and Blood Institute — Blood Transfusion
- World Health Organization — Blood safety and availability
- National Blood Transfusion Council, Government of India — National Blood Transfusion Council
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Blood Groups and Compatibility ExplainedHow ordinary blood groups are matched for transfusionDirected and Replacement DonationHow relatives can donate for a named patientWho Can Donate Blood: Eligibility in IndiaCheck whether you can join a rare donor listTransfusion and Blood DonationThe full guide to transfusion and donation
Talk to us
Unsure what your blood group report means?
Share your reports with us. A member of CION's haematology team will explain what they show and what to ask your blood bank.