There are several ways to find out your blood type, ranging from checking existing medical records to ordering a lab test or using an at-home kit. The fastest option is often one you already have access to: your birth certificate, a blood donor card, or your doctor’s office may already have your type on file.
Check Your Existing Records First
Before paying for any test, it’s worth checking whether your blood type has already been documented somewhere. Your birth certificate is a good place to start, since many hospitals record the baby’s blood type at birth. If it’s not there, your primary care doctor’s office may have it from a past blood draw or surgical workup. Call and ask.
If you’ve ever donated blood, your blood donor card lists your type. The same goes for military service records. And if you’ve had bloodwork done at a hospital or commercial lab in the past, you can call that lab directly to see if blood typing was part of the panel. Many people are surprised to learn their type was already tested and simply never communicated to them.
How a Lab Test Works
When none of your records have the answer, the standard approach is a blood draw at a lab or doctor’s office. The process is straightforward and uses a small sample of blood, typically from a vein in your arm.
Once collected, the sample is spun in a centrifuge to separate the red blood cells from the liquid portion (plasma). Then two sets of tests happen. In the first, called forward typing, your red blood cells are mixed with three different antibody solutions: one that reacts with A antigens, one that reacts with B antigens, and one that reacts with the Rh factor (the “positive” or “negative” part of your blood type). If your cells clump together when mixed with a particular antibody, it means that antigen is present on your cells. Clumping with anti-A but not anti-B means you’re type A. Clumping with both means AB. No clumping with either means type O.
The second step, reverse typing, works in the opposite direction. Your plasma is mixed with known A and B red blood cells to confirm which antibodies you naturally carry. Type A blood naturally contains anti-B antibodies, type B contains anti-A, type O contains both, and type AB contains neither. When both tests agree, the result is confirmed. The whole process takes minutes in a lab, and results are typically available within a day or two.
At-Home Blood Typing Kits
Home kits use the same basic principle as a lab test, just in a simplified format. You prick your finger, place drops of blood on a card pre-loaded with dried antibody reagents, and look for visible clumping. Clumping in a particular zone tells you which antigens your red blood cells carry.
These kits are widely available online and at some pharmacies for around $10 to $20. When used correctly, they’re accurate about 99.9% of the time. The key phrase is “when used correctly.” Errors typically come from not using enough blood, misreading the clumping reaction, or testing in temperatures outside the kit’s recommended range. If you get an ambiguous result (faint clumping that’s hard to interpret), it’s better to confirm with a lab test rather than guess.
Getting Tested Through a Lab or Blood Donation
If you’d rather have a professional handle it, you can order a blood type test directly from a commercial lab like Labcorp without a doctor’s order. Labcorp currently charges $39 for a standalone blood type test. Your doctor can also add blood typing to a routine blood draw, and insurance often covers it when it’s ordered for a medical reason (pregnancy, surgery prep, or a new patient workup).
Donating blood is another option that costs you nothing. Blood banks type every donation, and you’ll receive a donor card afterward that lists your ABO group and Rh status. If you’re eligible to donate, this is arguably the most useful way to learn your type, since you’re helping someone else in the process. The American Red Cross and most local blood banks provide your type within a few weeks of your first donation, either on a physical card or through an online donor portal.
What Your Results Mean
Your blood type is expressed as a combination of two systems. The ABO system classifies you as A, B, AB, or O based on which sugar molecules sit on the surface of your red blood cells. The Rh system adds “positive” or “negative” depending on whether you carry the RhD protein. Together, these give you one of eight common types: A+, A-, B+, B-, AB+, AB-, O+, or O-.
Type O negative is the universal red cell donor, meaning it can be given to almost anyone in an emergency. Type AB positive is the universal plasma donor. About 37% of the U.S. population is O positive, making it the most common type, while AB negative is the rarest at around 1%.
Why Rh Status Matters in Pregnancy
Knowing your Rh status is particularly important if you’re pregnant or planning to become pregnant. When an Rh-negative mother carries an Rh-positive baby, her immune system can recognize the baby’s blood cells as foreign and start producing antibodies against them. This doesn’t usually cause problems in a first pregnancy, but those antibodies persist. In a future pregnancy with another Rh-positive baby, they can cross the placenta and attack the baby’s red blood cells, leading to serious complications.
This is preventable. Rh-negative mothers receive an injection during pregnancy and after delivery that stops their immune system from forming those antibodies in the first place. The same treatment is recommended after a miscarriage, ectopic pregnancy, or abortion if the mother is Rh negative, since even small exposures to Rh-positive blood can trigger the immune response. This is one of the reasons blood typing is standard in early prenatal care.
Which Method to Choose
- Fastest and free: Check your birth certificate, call your doctor’s office, or look at a blood donor card you already have.
- Cheapest new test: An at-home kit ($10 to $20) gives reliable results if you follow the instructions carefully.
- Most reliable: A lab test ($39 without insurance, or covered when medically ordered) uses both forward and reverse typing to confirm the result.
- Most useful: Donating blood gets your type tested for free and helps someone who needs a transfusion.
For everyday knowledge, any of these methods works. If your blood type will be used for a medical decision like a transfusion or organ transplant, hospitals always run their own confirmatory test regardless of what you report, so there’s no safety risk in starting with a home kit or donor card to satisfy your curiosity.