You can find out your blood type at home using an inexpensive blood typing kit that requires just a finger prick and gives results in minutes. These kits are widely available online and at some pharmacies, typically costing between $8 and $20. They work by mixing a drop of your blood with dried antibodies on a card and checking for visible clumping patterns that reveal your type.
How Home Blood Typing Kits Work
The most common home kit is the EldonCard, which uses a small card containing dried antibody reagents in separate circles. You prick your finger, place drops of blood onto each circle, add water, and watch for clumping (called agglutination). Each circle tests for a different blood marker: one for the A antigen, one for the B antigen, and one for the Rh factor that determines whether you’re positive or negative.
The pattern of clumping tells you your type. If blood clumps only in the A circle, you’re type A. Only in the B circle, type B. Both A and B circles, type AB. If neither the A nor B circle shows clumping, you’re type O. The Rh circle then tells you whether you’re positive or negative. A fourth “control” circle on the card should never show clumping. If it does, the test is invalid and needs to be repeated.
The whole process takes about five minutes once you have the kit open.
How Accurate Are These Kits?
A study published in Military Medicine tested the EldonCard against FDA industry-standard lab procedures and found it produced accurate results under normal conditions. The kits held up well even in simulated field conditions with varying temperature and humidity. However, there are a few important caveats.
Storage matters. A competing kit (the ABO-Rh Combination Blood Typing Experiment Kit) lost accuracy after prolonged storage above 37°C (about 99°F), so if your kit has been sitting in a hot mailbox or garage, the results may not be reliable. When you order a kit online, try to retrieve it promptly rather than letting it bake on a doorstep in summer.
Weak reactions can also cause confusion. A small number of people have weak Rh antigens on their red blood cells, meaning the Rh circle might not show obvious clumping even though they’re technically Rh positive. Any test that produces faint or ambiguous clumping should be repeated. If you’re relying on your blood type for anything medically important, a home kit result is a good starting point but not a substitute for lab-confirmed typing.
Free Ways to Learn Your Blood Type
If you’d rather not buy a kit, donating blood is the easiest free option. The American Red Cross lets you create an online account where you can view your blood type after your first donation, along with results from the mini-physical they perform. Other blood banks and community blood drives typically mail or email your type within a few weeks of donating.
You can also check existing medical records. If you’ve ever had surgery, been pregnant, or been admitted to a hospital, your blood type was almost certainly tested. Your doctor’s office or the hospital’s medical records department can pull this information. Many patient portals now display past lab results, so it’s worth logging in and searching before ordering anything new.
Lab Testing Without a Doctor’s Order
If you want a professionally confirmed result but don’t want to schedule a doctor’s visit, direct-to-consumer lab testing is an option. Labcorp OnDemand offers a blood type test for $39 that you can order online and complete at any Labcorp location with a standard blood draw. Similar services exist through Quest Diagnostics and smaller lab networks. No prescription or referral is needed. You’ll get a definitive ABO and Rh result, which is the same test hospitals use.
Why Saliva Tests Aren’t Reliable
You may have seen claims that you can determine your blood type through a saliva sample. This is technically possible for some people, but not reliable enough to trust. About 87% of the population are “secretors,” meaning their blood type antigens show up in saliva and other body fluids. The remaining 13% are non-secretors whose saliva contains no usable blood type markers at all, so the test simply won’t work for them.
Even among secretors, saliva-based methods are less accurate than blood-based ones. Studies using the absorption inhibition technique on saliva found sensitivity ranging from 80% for type A to 87% for types O and B. That means roughly one in five to one in eight results could be wrong. Given that a finger-prick card test is just as easy and far more reliable, saliva testing isn’t worth the trade-off.
Understanding Your Results
Your blood type consists of two pieces of information: your ABO group (A, B, AB, or O) and your Rh factor (positive or negative). This gives you one of eight possible types. Type O positive is the most common in the United States, while AB negative is the rarest.
For everyday purposes, knowing your type is useful for blood donation, understanding potential pregnancy complications related to Rh incompatibility, and having the information ready in case of emergency. If you’re Rh negative and planning a pregnancy with an Rh positive partner, that’s something worth discussing with your healthcare provider, since it can affect future pregnancies if not managed.
Keep your confirmed blood type somewhere accessible, like a note in your phone or on an emergency card in your wallet. If you used a home kit and want extra confidence in the result, running a second card from a different kit box is a simple way to double-check before relying on it.