BloodTyper
Your Blood Type Reference
Comprehensive blood type information, calculators, and compatibility charts
Explore Blood Type Information
Access comprehensive tools and resources for understanding blood types, genetics, and compatibility
Blood Type Calculator
Calculate possible blood types for your child based on parent blood types
Compatibility Chart
Interactive matrix showing blood donation compatibility for all types
Rarity Information
Discover how common or rare different blood types are worldwide
Blood Types
Detailed information about all 8 blood types
Rh Factor Guide
Understanding Rh positive and negative blood types
Universal Types
Learn about universal donors and recipients
How to Find Your Blood Type
4 easy methods to discover your blood type quickly
Mosquitoes & Blood Type
Why mosquitoes prefer Type O blood - scientific facts
Why Blood Type Knowledge Matters
Understanding blood types isn't just academic—it can save lives
Emergency Transfusions
In emergencies, knowing your blood type can save critical time. Doctors need compatible blood for transfusions—receiving the wrong type can trigger a life-threatening immune reaction. Type O- blood is used in emergencies when there's no time to test, but only 7% of people have it. Carrying a blood type card or having it in your medical records can make the difference between life and death.
Critical fact: Wrong blood type transfusions can be fatal within minutes
Pregnancy & Rh Incompatibility
If a mother is Rh- and the father is Rh+, there's a risk of Rh incompatibility during pregnancy. The mother's immune system may attack the baby's Rh+ blood cells, causing hemolytic disease of the newborn (HDN). Knowing blood types early allows doctors to administer RhoGAM injections to prevent this condition. Untreated Rh incompatibility can lead to severe anemia, brain damage, or even fetal death.
Prevention is key: RhoGAM can prevent 98% of Rh complications when given on time
Blood Donation Impact
Certain blood types are in constant shortage. O-, O+, and B- donors are always needed because they can help more recipients. AB+ individuals are universal plasma donors—their plasma can save burn victims, trauma patients, and those with clotting disorders. Knowing your blood type helps blood banks target donors for specific needs. A single donation can save up to three lives.
Your impact: Every 2 seconds, someone in the U.S. needs blood
Frequently Asked Questions
Common questions about blood types answered
Can two O+ parents have an AB child?
No. Two O+ parents can only have O+ or O- children. Since both parents have only O alleles, they cannot pass A or B alleles to their child. The AB blood type requires one A allele and one B allele, which is impossible when both parents are type O.
What's the rarest blood type?
AB- (AB negative) is the rarest blood type, occurring in only about 1% of the global population. However, rarity varies by ethnicity—in some Asian populations, AB- occurs in less than 0.1% of people. The rarest blood types are highly valuable for blood donation.
Can your blood type change?
Very rarely. Your blood type is determined by your genes and typically stays the same throughout your life. However, in extremely rare cases, blood type can change after a bone marrow transplant, if you receive a transplant from a donor with a different blood type. Certain medical conditions affecting the bone marrow may also, in very rare instances, alter blood type expression.
Why is O- called the universal donor?
O- has no antigens. Since O- blood lacks A, B, and Rh antigens, it won't trigger an immune reaction in recipients of any blood type. This makes it safe to give to anyone in emergencies when there's no time to determine the recipient's blood type. However, O- individuals can only receive O- blood themselves.
What's the most common blood type?
O+ (O positive) is the most common blood type worldwide, found in approximately 37% of the global population. However, distribution varies by region—O+ is even more common in Hispanic and African populations (up to 53%), while A+ is more common in European populations.
Can a child have a different blood type than both parents?
Yes, absolutely. For example, two A+ parents (genotype AO) can have an O child if both pass their O allele. Similarly, an A parent and a B parent can have an O, A, B, or AB child. However, the child's blood type will always be compatible with the genetic possibilities from the parents' alleles.
Educational Blood Type Resources
Whether you're an expectant parent curious about your child's possible blood type, a student learning genetics, or preparing to donate blood, BloodTyper provides accurate, visual, and easy-to-understand information about blood type genetics and compatibility.