There are several ways to find out your blood type, ranging from a simple at-home card test to a standard lab draw. The fastest option for most people is an at-home kit that gives results in minutes, though a clinical lab test remains the most reliable method, especially if you need the result for a medical procedure.
The Eight Blood Types, Briefly
Your blood type is determined by tiny sugar molecules sitting on the surface of your red blood cells. If your cells carry the A sugar, you’re type A. If they carry the B sugar, you’re type B. If they carry both, you’re AB. If they carry neither, you’re type O. Each of those four groups is then split by a separate marker called the Rh factor, giving you eight possible types: A+, A−, B+, B−, AB+, AB−, O+, and O−.
Knowing your type matters most during blood transfusions, pregnancy, and organ donation. Outside of those situations, it’s still useful information to have on hand for emergencies.
At-Home Test Kits
The most common at-home option is a card-based kit like the EldonCard, which you can buy online for roughly $10 to $20. You prick your finger, place drops of blood on pre-treated areas of the card, and watch for clumping. The card contains dried antibodies that react with the A, B, and Rh markers on your red blood cells. If a spot clumps, the corresponding marker is present. Results appear within minutes.
These kits are designed to reduce the human error that can happen with traditional liquid-reagent testing on a glass plate. That said, they’re not considered clinical-grade. If you need a confirmed blood type for surgery, a blood donation, or pregnancy care, a lab test is the standard.
Lab and Clinical Testing
A clinical blood typing test is a straightforward blood draw. The lab mixes your sample with antibodies against A, B, and Rh antigens and checks for agglutination, which is the visible clumping that happens when antibodies latch onto matching markers on your red blood cells. Labs also run a “reverse type,” mixing your serum with known A and B red blood cells to confirm the result from the other direction.
You can request a blood type test through your primary care provider or order one directly from a lab. Based on data from actual patient charges between 2023 and 2024, the average out-of-pocket cost for ABO blood typing runs around $90 without insurance. Coverage varies by plan, so it’s worth checking with your insurer beforehand. Some people discover their blood type for free when they donate blood, since blood banks type every donation and typically share the result with you.
Free Options: Blood Donation and Medical Records
If you’ve ever donated blood, your blood type is already on file. Most blood banks include it on your donor card or in your online donor profile. This is one of the easiest and most reliable ways to find out, since the testing is done to clinical standards.
Your blood type may also be in your medical records if you’ve had surgery, been pregnant, or received a transfusion. Check your patient portal or call your doctor’s office. Many people already have this information sitting in their chart without realizing it.
Can DNA Tests Tell You Your Blood Type?
Some consumer DNA services do report blood type, but the approach is fundamentally different from a direct blood test. DNA tests look at your genes rather than physically checking what’s on your red blood cells. This can predict your likely blood type with reasonable accuracy, but it’s not a substitute for serological testing. Certain genetic variations, particularly less common subtypes of type A, can make gene-based predictions less precise. If a DNA test has given you a blood type result, treat it as a good estimate rather than a confirmed answer.
Guessing From Your Parents’ Blood Types
If you know both parents’ blood types, you can narrow down the possibilities, though you often can’t pin it to a single type. Blood type follows standard inheritance rules. Each parent passes one of their two ABO gene copies to you, and the combination determines your type.
- Two type O parents will always have type O children.
- Two type A parents can have children who are type A or type O. If both parents carry a hidden O gene (genotype AO), there’s a 75% chance of type A and a 25% chance of type O.
- One type A and one type B parent can produce children of any blood type: A, B, AB, or O, depending on each parent’s underlying genotype.
- One type AB parent means the child will always inherit at least one A or B gene, so type O is impossible.
The Rh factor follows a similar pattern. Two Rh-negative parents will always have Rh-negative children. If one or both parents are Rh-positive, the child can be either positive or negative, depending on whether the positive parent carries a hidden negative gene. Parent-based prediction can rule out certain blood types but rarely gives a definitive single answer.
Which Method to Choose
Your best option depends on why you need the information. If you’re just curious, an at-home card kit or checking old blood donation records is the simplest route. If you need a confirmed result for a medical reason, a lab test is the way to go. And if you’re about to have surgery or receive a transfusion, the hospital will type your blood regardless of what you already know, since clinical protocols require fresh confirmation every time.