Hemophilia Basics

You might already know a lot about hemophilia with inhibitors. But, just in case, let's cover some basics.


When a person bleeds, the body takes action to stop the bleed.3,7

Twelve different types of proteins work together to stop the bleed. They are called clotting factors.3

When someone is missing certain clotting factors, it's called hemophilia.3,4

Find out What Causes Bleeding >>

Learn about Types of Bleeds >>

Learn about Treating Bleeds >>

Understanding Hemophilia

A person with hemophilia will not bleed faster than anyone else — but they can bleed longer.3


  • Usually occurs in males
  • Is an X-chromosome-linked, genetically related bleeding disorder
  • Is caused by a deficiency of coagulation factor VIII or factor IX
  • Affects about 400,000 people worldwide

There is a family history of hemophilia in 70% of all cases. Hemophilia may occur with no family history in as many as 30% of patients.8

Types of Hemophilia

The two most common types of hemophilia are hemophilia A and hemophilia B.3

  • In hemophilia A, the blood has reduced levels of clotting factor VIII (factor eight).
  • In hemophilia B, the blood has reduced levels of clotting factor IX (factor nine). This is also called factor IX deficiency.

80%-85% of people with hemophilia have hemophilia A.4 Hemophilia is usually inherited.9

Acquired Hemophilia

While most people with hemophilia are born with it, some people do develop it over the course of their lifetime. When this happens, it is called acquired hemophilia. It is somewhat similar to hemophilia with inhibitors, since a person's body produces antibodies that prevent clotting factors in the blood from working.2

But, acquired hemophilia is also different from hemophilia with inhibitors. Acquired hemophilia is developed over the course of someone's life, but someone with hemophilia and inhibitors is born with hemophilia.2

Levels of Severity

Hemophilia types are generally grouped by the levels of clotting factors in the blood.4

  • Mild hemophilia usually means factor VIII or IX levels of 5%-40% of normal, with severe bleeding due to major trauma or surgery.
  • Moderate hemophilia usually means factor VIII or IX levels of 1%-5% of normal, with occasional bleeding that is not caused by an injury (also called spontaneous bleeding), or severe bleeding due to minor trauma or surgery.
  • Severe hemophilia usually means factor VIII or IX levels of < 1% of normal, with spontaneous bleeds (mostly in joints and muscles).

The severity of hemophilia does not usually change during a person's lifetime. People in the same family usually inherit the same level of severity of hemophilia.3

Diagnosing Hemophilia

To manage hemophilia properly, it has to be diagnosed accurately.4

Signs of hemophilia include4:

  • Easy bruising in early childhood
  • Spontaneous bleeding (especially in joints and muscles)
  • Excessive bleeding following an accident or surgery

Hemophilia and Inhibitors

Hemophilia is usually treated by taking factor VIII or factor IX replacement therapy. When someone has hemophilia with inhibitors, their body stops (inhibits) these factors from working.4

That's why different treatments are used to stop bleeds in patients with inhibitors. It's also important for you to take actions that prevent bleeds from happening.4

Learn about Treatment >>