There’s no single “best” blood type, but type O negative comes closest to earning that title. It’s the only blood type that can be safely transfused to virtually anyone in an emergency, and people with type O blood have measurably lower risks of heart disease, blood clots, and certain cancers compared to those with other blood types. That said, “best” depends on what you’re measuring. Each blood type has distinct advantages and disadvantages worth understanding.
Why O Negative Is the Universal Donor
When someone arrives at a hospital bleeding heavily and there’s no time to test their blood type, they receive O negative blood. Red blood cells in this type lack the A antigen, the B antigen, and the Rh protein, meaning virtually no recipient’s immune system will reject them. It’s the safest default option in trauma, surgery, and any situation where seconds count.
The catch: only about 7% of the population has O negative blood, creating a persistent supply problem. The American Red Cross declared an emergency blood shortage in July 2024 after its national inventory dropped more than 25%, and O positive and O negative were singled out as the most critically needed types. Because O negative is so universally useful, hospitals burn through it faster than donors can replace it.
Type O and Lower Disease Risk
Beyond its emergency usefulness, type O blood is linked to real health advantages. A study of 1.5 million blood donors published in Circulation found that people with non-O blood types (A, B, and AB) had significantly higher rates of dangerous blood clots. Compared to type O, non-O individuals were roughly twice as likely to develop deep vein thrombosis and 80% more likely to suffer a pulmonary embolism. The risk increase for heart attack and stroke was smaller but still statistically meaningful, at about 10% and 7% higher respectively.
The reason comes down to clotting proteins. People with A and B antigens on their red blood cells tend to have higher levels of a clotting factor that makes their blood more prone to forming dangerous clots. Type O blood naturally has lower levels of this protein.
Pancreatic Cancer Risk
Blood type also influences cancer risk, particularly for pancreatic cancer. Compared to type O, the odds of developing pancreatic cancer were 38% higher for type A, 47% higher for type AB, and 53% higher for type B. In raw numbers, the incidence rate for type O was about 29 cases per 100,000 people per year, while type B reached nearly 45 per 100,000. Researchers estimated that about 19.5% of all pancreatic cancer cases could be attributed to having a non-O blood type. For current smokers with non-O blood, the combined risk was particularly striking: 2.7 times higher than nonsmoking type O individuals.
Type O Offers Protection Against Severe Malaria
In regions where malaria is common, type O blood provides a powerful survival advantage. The malaria parasite works by infecting red blood cells, then causing those infected cells to clump together with healthy ones in clusters called “rosettes.” The A and B antigens on non-O red blood cells act like glue that strengthens these rosettes, helping the parasite spread more effectively through the bloodstream.
Type O red blood cells lack those antigens entirely, which reduces rosette formation by 60 to 70%. The result is dramatic: type O blood reduces the odds of severe malaria by about 66% compared to non-O types. This is one reason type O is the most common blood type in sub-Saharan Africa and other malaria-endemic regions. Thousands of years of evolutionary pressure selected for it.
Where AB Blood Has the Advantage
If you’re looking at “best” from the receiving end, AB positive wins. People with AB positive blood are universal recipients for red blood cell transfusions. Their red blood cells carry both A and B antigens, and the Rh protein, so their immune system recognizes all blood types as compatible. They produce neither anti-A nor anti-B antibodies, meaning no transfusion reaction regardless of the donor’s type.
AB blood also has a unique advantage when it comes to plasma, the liquid portion of blood used to treat burns, shock, and clotting disorders. Because AB plasma contains no anti-A or anti-B antibodies, it can be safely given to any patient regardless of their blood type. The NIH calls AB plasma “universal donor” plasma and refers to it as “liquid gold” because of its broad compatibility and value in emergency medicine. So while AB positive may carry higher disease risks for the person who has it, their donations are extraordinarily valuable to everyone else.
The Rarest Blood Type in the World
The rarest known blood type isn’t one of the familiar eight. It’s called Rh-null, sometimes referred to as “golden blood,” and only about 43 people in recorded history have ever been identified with it. Rh-null blood lacks all Rh antigens (there are over 60 of them, not just the positive/negative one most people know about), making it even more universally compatible than O negative for patients with rare Rh antibody combinations.
Living with Rh-null blood is a double-edged sword. Your donations are incredibly precious to the tiny number of people who need them, but receiving blood yourself is extremely dangerous. A transfusion from anyone who isn’t also Rh-null can trigger a severe reaction, including kidney failure. People with golden blood essentially depend on a global network of fewer than 50 known donors.
What “Best” Really Means for You
If you’re wondering whether your blood type puts you at a health advantage or disadvantage, here’s the practical picture. Type O correlates with lower cardiovascular risk, lower cancer risk for certain types, and better malaria resistance. But these are population-level statistics, not destiny. A type A person who exercises, doesn’t smoke, and eats well will almost certainly outlive a sedentary type O person with poor habits. Blood type is one variable among hundreds that shape your health.
From a medical system perspective, the “best” blood to have is whichever type is needed most at any given moment. O negative and O positive are perpetually in short supply because they’re used so heavily in emergencies. AB plasma is always in demand. If you’re eligible to donate, your specific type fills a gap that no other type can.