How to Determine Your Blood Type
Ask your parents for their blood type., Call a doctor who has drawn your blood., Buy a blood typing kit.
Step-by-Step Guide
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Step 1: Ask your parents for their blood type.
If your biological parents both know their blood type, that narrows down the possibilities.
In most cases this is only enough to guess, using an online blood type calculator or the following list:
O parent x O parent = O child O parent x A parent = A or O child O parent x B parent = B or O child O parent x AB parent = A or B child A parent x A parent = A or O child A parent x B parent = A, B, AB or O child A parent x AB parent = A, B or AB child B parent x B parent = B or O child B parent x AB parent = A, B or AB child AB parent x AB parent = A, B or AB child Blood types also include an "Rh factor" (+ or
-).
If both of your parents have an Rh- blood type (such as O- or AB-), you are also Rh-.
If one or both of your parents are Rh+, you cannot tell whether you are + or
- without a test. -
Step 2: Call a doctor who has drawn your blood.
If your physician already has your blood type on file, then you just need to ask.
However, they will only have your record on file if you've already had your blood drawn and/or tested.
Common reasons why you may have already had your blood type tested include:
Pregnancy Surgery Organ donation Blood transfusion , If you don't want to visit a doctor or donate blood, you can find a home test kit online or at a pharmacy for as little as US $10.
These typically instruct you to dampen various labeled patches on a special card, then prick your finger and add a little blood to each patch.
Make sure to follow the kit instructions when adding the blood.
Note which patches (or vials of fluid, in some kits) cause the blood to clump (agglutinate) instead of spreading out.
The clumping is a reaction to substances incompatible with your blood type.
Once you've completed the test with all cards or fluids, look up your blood type using the kit instructions or the following list:
First check the "Anti-A" and "Anti-B" patches for clumps:
Clumps in Anti-A (only) mean you have type A blood.
Clumps in Anti-B mean you have type B blood.
Clumps in Anti-A and Anti-B: you are type AB.
Then check the "Anti-D" patch:
Clumps: you are Rh positive.
Add a + to your blood type.
No clumps: you are Rh negative.
Add a
- to your blood type.
If the control patch (normal paper) causes clumping, or if you are not sure whether the blood is clumping on any patch, try another card.Any test conducted at home is less reliable than a test performed by a professional. -
Step 3: Buy a blood typing kit.
Detailed Guide
If your biological parents both know their blood type, that narrows down the possibilities.
In most cases this is only enough to guess, using an online blood type calculator or the following list:
O parent x O parent = O child O parent x A parent = A or O child O parent x B parent = B or O child O parent x AB parent = A or B child A parent x A parent = A or O child A parent x B parent = A, B, AB or O child A parent x AB parent = A, B or AB child B parent x B parent = B or O child B parent x AB parent = A, B or AB child AB parent x AB parent = A, B or AB child Blood types also include an "Rh factor" (+ or
-).
If both of your parents have an Rh- blood type (such as O- or AB-), you are also Rh-.
If one or both of your parents are Rh+, you cannot tell whether you are + or
- without a test.
If your physician already has your blood type on file, then you just need to ask.
However, they will only have your record on file if you've already had your blood drawn and/or tested.
Common reasons why you may have already had your blood type tested include:
Pregnancy Surgery Organ donation Blood transfusion , If you don't want to visit a doctor or donate blood, you can find a home test kit online or at a pharmacy for as little as US $10.
These typically instruct you to dampen various labeled patches on a special card, then prick your finger and add a little blood to each patch.
Make sure to follow the kit instructions when adding the blood.
Note which patches (or vials of fluid, in some kits) cause the blood to clump (agglutinate) instead of spreading out.
The clumping is a reaction to substances incompatible with your blood type.
Once you've completed the test with all cards or fluids, look up your blood type using the kit instructions or the following list:
First check the "Anti-A" and "Anti-B" patches for clumps:
Clumps in Anti-A (only) mean you have type A blood.
Clumps in Anti-B mean you have type B blood.
Clumps in Anti-A and Anti-B: you are type AB.
Then check the "Anti-D" patch:
Clumps: you are Rh positive.
Add a + to your blood type.
No clumps: you are Rh negative.
Add a
- to your blood type.
If the control patch (normal paper) causes clumping, or if you are not sure whether the blood is clumping on any patch, try another card.Any test conducted at home is less reliable than a test performed by a professional.
About the Author
Emma Gibson
Creates helpful guides on lifestyle to inspire and educate readers.
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