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Your genotype and your blood group are two completely different things. In everyday UK usage — particularly for families with African or Caribbean heritage — “genotype” almost always means your haemoglobin genotype (results such as AA, AS, AC or SS), which tells you about your sickle cell status. Your blood group (such as O positive or A negative) is something else entirely: it describes markers on your red blood cells and matters mainly for blood transfusions and pregnancy.
The two are inherited separately, tested separately, and one cannot be worked out from the other. Knowing that you are blood group O positive tells you nothing about whether your genotype is AA, AS or SS — and knowing your genotype tells you nothing about your blood group.
| Haemoglobin genotype | Blood group (blood type) | |
|---|---|---|
| What it describes | The type of haemoglobin (the oxygen-carrying protein) in your red blood cells | The antigens (markers) on the surface of your red blood cells |
| Common results | AA, AS, AC, SS, SC | A, B, AB or O — each either positive or negative (e.g. O positive) |
| Mainly used for | Understanding sickle cell status and family planning | Safe blood transfusion and pregnancy care |
| Gene involved | The haemoglobin (beta-globin) gene | The ABO gene and the Rh gene — separate genes on a different chromosome |
| How it is tested | Haemoglobin electrophoresis (or a similar laboratory method) | Blood typing (ABO and Rh grouping) |
| Can it change? | No — fixed for life in normal circumstances | No — fixed for life in normal circumstances |
When people in the UK talk about “checking their genotype”, they usually mean their haemoglobin genotype. Haemoglobin is the protein inside red blood cells that carries oxygen around the body and gives blood its red colour. Normal adult haemoglobin is called haemoglobin A.
You inherit one haemoglobin gene from each parent, so your result is written as two letters:
This is why genotype matters so much for family planning rather than for transfusions. If you’d like the meaning of each result explained in full, see our detailed guide to what your AA, AS, AC and SS genotype results mean. For the medical background on carrier status, the NHS has clear information on being a sickle cell carrier.
Your blood group is a different classification altogether. It is based on antigens — combinations of sugars and proteins — on the surface of your red blood cells, along with matching antibodies in your plasma.
Two systems make up your everyday blood group:
Together they produce the eight main blood groups: A+, A−, B+, B−, AB+, AB−, O+ and O−. According to NHS Blood and Transplant, group O is the most common in the UK. Your blood group is inherited from your parents and is mainly important when you need a transfusion or during pregnancy.
The confusion is understandable, and it usually comes down to the letters. Both systems use letters — and both use the letter “A”. But an “A” in a genotype result means something completely different from an “A” in a blood group.
So genotype AA is not the same as blood group A. A person with genotype AA could have blood group A, B, AB or O. They are two separate results that happen to share a letter.
No. This is the single most important point, and it is where most online explanations go wrong. Haemoglobin genotype and ABO/Rh blood group are controlled by different genes, carried on different chromosomes, and inherited independently of each other.
Because of that, there is no shortcut: you cannot look at your blood group and calculate your genotype, and you cannot look at your genotype and calculate your blood group. The only way to know each one is to test for it directly.
This is one of the most common questions people ask, and the honest answer is: your genotype result alone cannot tell you. Someone with genotype AA can be O positive, A negative, B positive, AB positive, or any other blood group. The same is true for AS, AC and every other genotype.
In other words, every combination is possible — genotype AA with O positive, AS with O positive, AA with A negative, and so on — because the two are decided by separate genes. If you know one and want to know the other, you simply need the second test.
Both results come from a routine blood sample, but the laboratory does different things with it:
In the UK, a blood test to check whether you carry the sickle cell trait is available free through your GP surgery or a sickle cell and thalassaemia centre, and newborns are screened as part of the national programme. You can also arrange testing privately if you would prefer not to wait. If you want the full step-by-step, see our guide on how to check your genotype in the UK, or book a genotype (haemoglobin) blood test or a blood group test directly.
In normal circumstances, no. Both your haemoglobin genotype and your blood group are inherited and stay the same throughout your life. If a test result appears to have “changed”, it is far more likely that an earlier result was recorded incorrectly, that a different test was done, or that the two results are being confused with one another.
The rare exception worth knowing is that a bone marrow or stem cell transplant — a specialist treatment — can change the haemoglobin produced by the blood-forming cells. This does not happen with everyday life, diet or medication.
There is no single “best” blood group. Each is simply a different type, and blood services need donors from every group. Being one group rather than another does not make you healthier.
Haemoglobin genotype is better thought of in terms of health information rather than “good” or “bad”. Genotype AA means you do not carry a sickle cell or haemoglobin C gene. AS and AC are carrier (trait) states — most carriers are healthy but can pass a gene to their children. SS and SC are forms of sickle cell disease, which needs specialist care from the NHS. The real value is not in having a “better” result, but in knowing your status — especially before planning a family. You can read more from the NHS about sickle cell disease.
Knowing both results can be useful, but genotype in particular tends to matter most when:
If you and a partner are both carriers, it is worth understanding the odds together before conceiving — our guide to genotype compatibility for couples planning a family explains the combinations in detail.
Ready to find out your status? You can book a genotype (haemoglobin) blood test or a blood group test with Swift Blood Tests and get clear, professional results.
This article is for general education and is not a substitute for personal medical advice. If you have questions about your own results or family planning, speak to your GP or a qualified healthcare professional.
No. Genotype (in everyday UK use) refers to your haemoglobin type, such as AA, AS or SS, and relates to sickle cell status. Blood group refers to the ABO and Rh antigens on your red blood cells, such as O positive. They are separate results with separate uses.
No. The two are controlled by different genes and inherited independently, so your blood group cannot reveal your genotype and your genotype cannot reveal your blood group. Each has to be tested for directly.
Your genotype alone cannot tell you. Someone with genotype AA can have any blood group — O positive, A negative, B positive and so on — because blood group is decided by separate genes. You would need a blood group test to find out.
AA is a genotype result (referring to haemoglobin), not a blood group. Blood groups are written as A, B, AB or O with a positive or negative Rh status.
In normal circumstances, no — both are inherited and stay the same for life. The only notable exception is that a bone marrow or stem cell transplant can change the haemoglobin produced by the blood, which is a specialist medical situation.
There is no “best” blood group — each is simply a different type. For genotype, the useful thing is knowing your status rather than aiming for a particular result. AA means you are not a carrier, AS and AC are carrier states, and SS and SC are forms of sickle cell disease that need specialist care.
