You can find out your blood type through a doctor’s office blood draw, a home testing kit, donating blood, or by checking your existing medical records. The simplest option depends on how quickly you need the answer and whether you want to spend any money. Most people fall into one of eight blood types, and the test itself takes only minutes.
Check Your Medical Records First
If you’ve ever had surgery, donated blood, or been pregnant, your blood type is likely already on file somewhere. This is the fastest and cheapest way to get your answer without any new testing. Start by logging into your healthcare provider’s online patient portal, where lab results are typically stored. If you don’t have portal access, call your provider’s office and ask for the health information services department or the administrative staff who handles medical record requests. You may need to fill out a release form, send an email, or fax a written request.
If you gave birth in a hospital, your prenatal records will include your blood type because it’s tested during the first trimester of every pregnancy. Blood donation organizations also keep your type on file, so if you’ve ever donated, check any cards or correspondence they sent you.
Order a Lab Test Through Your Doctor
The standard medical blood type test is called ABO typing, and it works in two steps. In the first step (forward typing), a small blood sample is mixed with antibodies against type A and type B blood. Lab technicians watch to see whether your red blood cells clump together in response. If they clump when exposed to anti-A antibodies, you have type A. If they clump with anti-B, you have type B. If they clump with both, you’re type AB. If neither causes clumping, you’re type O.
The second step, called back typing, works in reverse. The liquid portion of your blood (with the cells removed) is mixed with known A and B blood cells to confirm the result. A separate test using the same clumping method determines your Rh factor, the “positive” or “negative” part of your blood type. Rh refers to a specific protein on the surface of red blood cells. If you have it, you’re Rh positive. If you don’t, you’re Rh negative.
Your doctor can order this test as part of routine bloodwork. If you’d rather skip the doctor visit, direct-to-consumer lab services like Labcorp OnDemand offer a blood type test for around $39 without a prescription. You order online, visit a local lab for the blood draw, and get results electronically.
Use a Home Testing Kit
Home blood typing kits let you test yourself with a finger prick. The most widely used version, the EldonCard, is a small plastic card with dried antibody patches on its surface. You place drops of blood on each patch and watch for clumping, which tells you your ABO group and Rh status. The whole process takes a few minutes.
These kits are surprisingly reliable. The EldonCard has been tested against standard laboratory blood typing procedures at multiple labs in different countries, showing 99.9% agreement with professional results. The kits use monoclonal antibodies, the same type of targeted antibodies used in clinical settings, just applied to a card format instead of a test tube. Home kits typically cost between $10 and $20 and are available online. They’re a good option if you’re curious about your blood type but don’t have an immediate medical need for the information.
Donate Blood
Every blood donation is typed as part of standard processing. If you’ve never donated before, this is a way to find out your blood type while doing something useful. After your donation, the blood center will notify you of your type, often through a donor card, an app, or an online account. The turnaround time varies by organization but is usually within a few weeks of your first donation.
Why Your Blood Type Matters
Knowing your blood type becomes important in a few specific situations. The most urgent is blood transfusions. Receiving the wrong type can trigger a dangerous immune reaction, which is why hospitals always type your blood before a transfusion, even if you already know your type. Organ transplantation also requires blood type compatibility between donor and recipient.
Pregnancy is another key scenario. If you’re Rh negative and your baby is Rh positive (inheriting the Rh protein from the other parent), your immune system can produce antibodies that attack the baby’s red blood cells. This is why blood typing is one of the first tests done during prenatal care. If the mismatch is caught early, medication given during pregnancy can prevent antibody development and protect the baby.
The Eight Blood Types and How Common They Are
Your blood type is determined by two things: your ABO group (A, B, AB, or O) and your Rh factor (positive or negative). That creates eight possible combinations, and they’re not equally common. Based on donor data from NHS Blood Donation:
- O positive: 36% (the most common)
- A positive: 28%
- O negative: 14%
- B positive: 8%
- A negative: 8%
- B negative: 3%
- AB positive: 2%
- AB negative: 1% (the rarest)
These percentages shift somewhat across ethnic groups and geographic regions, but the overall pattern holds: O and A types together account for the vast majority of the population, while AB negative is consistently the rarest. O negative blood is sometimes called the “universal donor” type because it can be given to patients of any blood type in an emergency, which is why blood banks are always looking for O negative donors.
Your blood type is inherited from your parents and stays the same for life, so you only need to find it out once. Whichever method you choose, the result is permanent and worth keeping in your personal health records.