Hemophilia is a disorder where your blood does not clot normally

Hemophilia is a genetic condition in which your blood lacks enough of a protein called a clotting factor. When you bleed—from an injury, surgery, or sometimes for no obvious reason—your body cannot form a clot quickly enough to stop the bleeding. The bleeding may be minor, like a nosebleed that lasts longer than usual, or serious, like bleeding inside a joint or the brain.

There are two main types: hemophilia A, caused by low levels of clotting factor VIII, and hemophilia B, caused by low levels of clotting factor IX. Both are inherited conditions passed down through families, usually from parent to child. Hemophilia A is more common, accounting for about 80 percent of cases.

The severity depends on how much clotting factor your body produces. Some people have mild hemophilia and bleed only after injury or surgery. Others have severe hemophilia and can bleed spontaneously—without any obvious trigger—into joints, muscles, or organs.

Key Takeaways

  • Hemophilia is an inherited disorder where your blood lacks enough clotting factor VIII or IX, preventing normal clot formation.
  • Hemophilia A is caused by low factor VIII and is more common; hemophilia B is caused by low factor IX.
  • Severity ranges from mild (bleeding only after injury) to severe (spontaneous bleeding into joints and organs).
  • Treatment involves replacing the missing clotting factor through infusions, which can be done at home or in a clinic.
  • With proper treatment and care, most people with hemophilia can live normal lifespans and participate in most activities.

How your body normally stops bleeding

When you cut yourself, your body goes through a series of steps to seal the wound. First, platelets—tiny cells in your blood—rush to the injury and stick together to form a plug. Then clotting factors, which are proteins in your blood plasma, work together in a chain reaction to form fibrin, a mesh-like substance that strengthens the plug into a solid clot.

In hemophilia, one of the clotting factors in this chain is missing or too low. The chain breaks, and the clot forms too slowly or not at all. A small cut that would normally stop bleeding in a few minutes might bleed for hours. A bump that would cause minor bruising in most people might cause bleeding deep inside a joint or muscle.

Symptoms depend on how severe your hemophilia is

In mild hemophilia, you might not notice symptoms until you have surgery, a dental procedure, or a significant injury. You may experience unusual bruising, nosebleeds that last longer than expected, or heavy bleeding after a cut.

In moderate hemophilia, you may have spontaneous bleeding occasionally, along with prolonged bleeding after injury. In severe hemophilia, spontaneous bleeding is common. You might wake up with a swollen, painful joint or notice bruising without remembering an injury. Bleeding can occur in muscles, joints (especially knees, elbows, and ankles), the gastrointestinal tract, or the brain—all of which require urgent treatment.

Some people notice symptoms in infancy or early childhood: excessive bleeding after circumcision, unusual bruising as a baby begins to crawl or walk, or bleeding into joints that causes pain and swelling. Others do not discover they have hemophilia until adulthood, when they bleed heavily during surgery or after an accident.

Hemophilia is inherited, but not everyone in a family has it

Hemophilia is an X-linked recessive condition, meaning the gene that causes it sits on the X chromosome. Males have one X chromosome and one Y chromosome; females have two X chromosomes. A male who inherits the hemophilia gene on his single X chromosome will have hemophilia. A female who inherits the gene on one X chromosome is usually a carrier—she has one normal copy and one mutated copy—and typically does not have symptoms, though some carriers do experience mild bleeding problems.

If your mother is a carrier, each of her sons has a 50 percent chance of inheriting hemophilia, and each of her daughters has a 50 percent chance of being a carrier. If your father has hemophilia, all of his daughters will be carriers, and none of his sons will have hemophilia (because they inherit the Y chromosome from him, not the X).

In about one-third of hemophilia cases, there is no family history. The condition arose from a new genetic mutation in that person. If you have hemophilia and want to have children, genetic counseling can help you understand the risk to your children and your partner's risk of being a carrier.

Treatment replaces the missing clotting factor

The standard treatment for hemophilia is factor replacement therapy. You receive infusions of clotting factor—either factor VIII or factor IX, depending on which type of hemophilia you have—through a vein. The infusion delivers the missing protein directly into your bloodstream, allowing your blood to clot normally for a period of time.

Factor products come from two sources: plasma-derived (made from donated human blood plasma) or recombinant (made in a laboratory using genetic engineering). Both are effective and safe. Recombinant products carry no risk of bloodborne infection because they are not made from human blood.

Some people use factor on-demand, meaning they infuse only when they bleed or before a procedure. Others use prophylactic treatment, meaning they infuse regularly on a schedule to prevent bleeding before it starts. Prophylactic treatment is more common in severe hemophilia because it reduces the number of bleeding episodes and prevents joint damage over time.

Many people with hemophilia learn to infuse themselves or are taught to do so by a family member. Home infusion is convenient and allows you to treat bleeding quickly, which reduces pain and prevents complications. Others receive infusions at a hemophilia treatment center or hospital.

Living with hemophilia means planning ahead for activities and procedures

With proper treatment, most people with hemophilia can work, go to school, exercise, and participate in most daily activities. Contact sports like football or hockey carry higher risk of injury and bleeding, but many people with hemophilia play sports with appropriate protective gear and medical supervision.

Before any medical or dental procedure—even a routine cleaning—tell your healthcare provider that you have hemophilia. They will coordinate with your hemophilia treatment center to ensure you receive factor replacement before and after the procedure to prevent excessive bleeding.

Certain medications can increase bleeding risk and should be avoided. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) thin the blood and can worsen bleeding; acetaminophen is usually a safer choice for pain. Your hemophilia team can advise you on which medications are safe.

Regular visits to a hemophilia treatment center—ideally a comprehensive center with hematologists, nurses, physical therapists, and social workers—help prevent complications, manage joint damage, and adjust your treatment plan as your needs change.

Complications can develop over time without proper treatment

Repeated bleeding into joints—called hemarthrosis—can damage the cartilage and bone, leading to chronic pain, swelling, and reduced movement. This is one of the most common long-term complications of hemophilia. Physical therapy and consistent factor replacement help prevent or slow this damage.

Some people develop inhibitors, which are antibodies that attack the clotting factor you infuse, making it less effective or useless. Inhibitors develop in about 30 percent of people with hemophilia A and 5 percent of people with hemophilia B. If you develop an inhibitor, your treatment changes to either higher doses of factor or different products designed to bypass the inhibitor.

Before modern treatment, people with hemophilia who received blood products faced risk of infection with hepatitis C or HIV. Today's blood products are screened and treated to remove viruses, and recombinant products carry no such risk. However, some people treated before screening was routine may have been infected and should be tested.

Frequently Asked Questions

Can women have hemophilia?

Yes, though it is rare. A woman can have hemophilia if she inherits the hemophilia gene from both parents or if she has Turner syndrome (one X chromosome instead of two). More commonly, women are carriers—they have one copy of the gene and may experience mild bleeding symptoms. Some female carriers have bleeding problems severe enough to require treatment.

Is hemophilia curable?

Currently, hemophilia is not curable with standard treatments, but gene therapy is emerging as a potential cure. Gene therapy involves modifying your cells to produce clotting factor on their own. Several gene therapies have been approved or are in late-stage testing, though they are not yet widely available and are very expensive.

Can someone with hemophilia donate blood?

No. People with hemophilia should not donate blood because their blood lacks clotting factor and could harm recipients. Blood banks screen for hemophilia and will not accept donations from people with the condition.

What is the life expectancy for someone with hemophilia?

With modern treatment, most people with hemophilia have a normal or near-normal lifespan. Life expectancy depends on access to treatment, adherence to prophylactic therapy, and how well complications like joint damage and inhibitors are managed. People without access to treatment face much shorter lifespans and higher rates of disability.

Does hemophilia get worse over time?

Hemophilia itself does not worsen—the amount of clotting factor your body produces stays the same throughout life. However, repeated bleeding into joints can cause progressive damage and pain if not prevented with consistent factor replacement. Proper treatment prevents this progression.