Hemophilia and bleeding disorders: Full guide

What is hemophilia?

Hemophilia is a condition where the blood does not clot the way it should. Clotting is how your body stops bleeding. It depends on proteins in the blood called clotting factors. In hemophilia, one of these factors is missing or too low.

There are two main kinds. Hemophilia A means low factor VIII (factor 8). Hemophilia B means low factor IX (factor 9). Hemophilia A is about four to five times more common.

Hemophilia is usually inherited, which means it is passed down in families through genes. The genes for factor VIII and factor IX are on the X chromosome. Because of this, hemophilia mostly affects boys and men. Girls and women can be carriers, and some carriers have bleeding problems too.

People with hemophilia do not bleed faster than others. They bleed longer. The most typical problem is bleeding inside joints, like the knees, ankles, and elbows. Over time, repeated joint bleeds can damage the joint. Bleeding in muscles and, rarely, in the brain can also happen.

Hemophilia is not cancer and it is not contagious. It is a lifelong condition, but treatment has changed a great deal. Most people now take regular treatment to prevent bleeds before they start. Many can play, work, and travel like anyone else.

Types of bleeding disorders

Hemophilia A

Caused by low or missing factor VIII. It is the most common type of hemophilia.

Hemophilia B

Caused by low or missing factor IX. It is less common than hemophilia A. The symptoms look the same, but some treatments are different.

Carriers and women with hemophilia

Women and girls who carry the gene can have factor levels from very low to normal. About a quarter to a third have low enough levels to bleed more than usual. This can mean heavy periods, bleeding after childbirth, or bleeding after dental work or surgery. They deserve testing and care too.

Von Willebrand disease

The most common inherited bleeding disorder. It affects both men and women. Von Willebrand factor helps platelets stick together and carries factor VIII. It usually causes nosebleeds, easy bruising, heavy periods, and bleeding after surgery or dental work. It is often treated with desmopressin, tranexamic acid, or factor concentrates that contain von Willebrand factor.

Acquired hemophilia A

A rare condition where the immune system makes an antibody against factor VIII later in life. It is not inherited. It most often happens in older adults or after childbirth. It causes large bruises and muscle bleeding and needs urgent treatment.

Hemophilia with an inhibitor

Some people make antibodies, called inhibitors, against the factor they are given. Inhibitors make factor treatment work poorly or not at all. They are more common in severe hemophilia A. Other treatments work well in this case.

Other rare factor deficiencies

Low levels of other clotting factors, such as factor VII, X, XI, or XIII, are rare bleeding disorders. A hematologist can test for them if the cause of bleeding is not clear.

Tests you may have

Family history

Your care team will ask about bleeding in your family. About a third of babies with hemophilia have no known family history, because the gene change can be new.

aPTT and PT

Screening blood tests that measure how long blood takes to clot. In hemophilia, the aPTT is usually long and the PT is normal. Mild hemophilia can still have a normal aPTT.

Factor VIII and factor IX levels

Blood tests that measure how much of each factor you have, as a percent of normal. This confirms the diagnosis and tells how severe it is.

Von Willebrand tests

Blood tests that measure von Willebrand factor and how well it works. They help tell von Willebrand disease apart from mild hemophilia A.

Genetic testing

A blood test that finds the exact gene change. It can help predict the risk of inhibitors, confirm whether a woman is a carrier, and guide family planning.

Inhibitor testing

A blood test, called the Bethesda assay, checks for antibodies against factor. It is done regularly, especially in the early years of treatment, and if factor stops working as well.

Joint exams and imaging

A physical therapist or doctor checks your joints. Ultrasound or MRI can find joint damage or bleeding early.

Testing during pregnancy and at birth

Carriers who are pregnant can plan testing and delivery with their care team. Babies at risk can be tested at birth with a blood sample, often from the umbilical cord.

How serious it is

Hemophilia is grouped by how much clotting factor is in your blood, compared with a normal level of 100 percent. The lower the level, the more likely bleeding is. Severity usually stays the same over a person's life and is often the same within a family.

Severe (factor level below 1 percent)

Bleeding can happen with no injury at all, often into joints and muscles. It is often found in babies or toddlers. Regular preventive treatment is the standard.

Moderate (1 to 5 percent)

Bleeding usually follows a minor injury, but it can sometimes happen on its own. Many people benefit from preventive treatment.

Mild (more than 5 percent up to 40 percent)

Bleeding mostly happens with surgery, dental work, or a major injury. Some people are not diagnosed until adulthood. Treatment is often given only when needed.

Target joint

A joint that bleeds again and again. Without good prevention, it can lead to lasting joint damage, called hemophilic arthropathy.

Bleeding in the head

The most dangerous kind of bleed. Any head injury in a person with hemophilia needs treatment right away, even if they feel fine.

Lab tests to know

A few lab results guide your treatment plan. Ask your care team to write down your type, baseline factor level, and inhibitor status. Keep it with you.

Baseline factor level

Your natural factor VIII or IX level. It sets your severity and helps plan treatment for bleeds and surgery.

Factor recovery and trough levels

Tests after a dose of factor show how high your level goes and how long it stays up. This helps fit your treatment schedule to you.

Inhibitor titer (Bethesda units)

Measures how strong an inhibitor is. A low titer may be overcome with more factor. A high titer needs a different kind of treatment.

Tests while taking emicizumab

Emicizumab makes the aPTT test and some factor VIII tests look falsely normal. Labs must use a special test (a chromogenic assay that uses bovine reagents) to measure factor VIII or inhibitors. Tell every lab and hospital that you take it.

Antithrombin level

If you take fitusiran, your antithrombin level is checked. This helps set your dose and lower the risk of blood clots.

Liver tests

Checked before and after gene therapy, because gene therapy works through the liver and can cause liver inflammation.

Carrier factor levels

Women who carry the gene should know their own factor level, especially before surgery, dental work, or childbirth.

Main treatments

Hemophilia treatment centers

Special clinics with a team of hematologists, nurses, physical therapists, social workers, and others. Care at one of these centers is linked to better health. Ask to be connected to one.

Prophylaxis (preventive treatment)

Regular treatment on a schedule to keep bleeds from happening. It is the standard for severe hemophilia and many moderate cases. Starting early in childhood protects the joints. Adults also benefit.

Factor replacement

The missing factor VIII or IX is given through a vein. It can be made in a lab (recombinant) or from donated plasma. Many people learn to give it at home. It is used both to prevent bleeds and to treat them.

Extended half-life factor

Newer factor products last longer in the blood, so people need fewer infusions. For example, efanesoctocog alfa (Altuviiio) for hemophilia A can be given once a week. Some factor IX products can be given every 1 to 2 weeks.

Emicizumab (Hemlibra)

A shot under the skin for hemophilia A, with or without inhibitors. It does the job of factor VIII by bringing two other clotting factors together. It is given every 1, 2, or 4 weeks. It does not work for hemophilia B. It is used only to prevent bleeds, so you still need a plan for treating breakthrough bleeds.

Newer rebalancing medicines

These shots lower the body's natural anti-clotting proteins so blood can clot better. Fitusiran (Qfitlia) lowers antithrombin and is given every 1 to 2 months. Concizumab (Alhemo) and marstacimab (Hympavzi) block a protein called TFPI. They work for hemophilia A or B, including people with inhibitors. They carry a risk of blood clots, so they need careful monitoring.

Gene therapy

A one-time IV treatment that gives the liver a working copy of the factor gene. Then the body can make its own factor. Etranacogene dezaparvovec (Hemgenix) is approved for adults with hemophilia B, and most people can stop regular preventive treatment. A hemophilia A gene therapy (Roctavian) was taken off the US market in 2026. Gene therapy is not used for people with an inhibitor and is only offered at special centers.

Bypassing agents

For people with inhibitors, medicines called recombinant factor VIIa and aPCC (FEIBA) help blood clot by going around the missing factor. They are used to treat bleeds. Do not use aPCC with emicizumab unless your hematologist directs it, because the combination caused serious clotting problems.

Immune tolerance induction

For people with inhibitors, frequent factor infusions over months can train the immune system to stop making the inhibitor. It works in up to about two thirds of people with hemophilia A.

Desmopressin and tranexamic acid

Desmopressin (DDAVP) is a nasal spray or shot that releases stored factor VIII and von Willebrand factor. It can help some people with mild or moderate hemophilia A and many with von Willebrand disease, but not hemophilia B. Tranexamic acid is a pill or liquid that helps clots hold, useful for mouth, nose, and heavy period bleeding.

Treatment side effects and what helps

Inhibitors

The main problem with factor treatment. Signs include bleeds that do not stop as expected after factor. Regular inhibitor testing finds them early. Tell your care team if your treatment seems to work less well.

Allergic reactions

Rarely, factor products can cause hives, swelling, or trouble breathing. This is more common in hemophilia B with an inhibitor. Get help right away for any serious reaction.

Vein access problems

Frequent infusions can be hard, especially in young children. Some children need a port, a small device placed under the skin. Shots under the skin, like emicizumab, can make treatment easier.

Injection site reactions

Shots under the skin may cause redness, itching, or soreness. Rotating the injection site helps.

Blood clots

Rebalancing medicines, and aPCC combined with emicizumab, can raise the risk of blood clots. Follow your dosing plan and lab checks closely. Call for leg swelling, chest pain, sudden shortness of breath, or a severe headache.

Liver inflammation after gene therapy

Liver enzymes can rise in the months after gene therapy. You will have frequent blood tests, and some people need steroids for a time. Avoid alcohol as your care team advises.

Gallbladder and liver effects from fitusiran

Fitusiran can cause gallbladder problems and changes in liver tests. Report pain in the upper right belly or yellow skin.

Desmopressin side effects

Flushing, headache, and fluid build-up. It can lower your sodium, so limit fluids as instructed while using it. It works less well after a few doses in a row.

Living with hemophilia

With today's treatments, many people with hemophilia have few or no bleeds. Children can go to school, play, and grow up to have careers and families. The key is regular prevention, a clear plan for bleeds, and a strong team.

Know your bleeding plan. Learn the early signs of a joint bleed, such as tingling, warmth, stiffness, or pain. Treat early, and use rest, ice, compression, and raising the limb as your care team advises. Keep a log of bleeds and treatments, on paper or in an app.

Stay active. Swimming, biking, and walking strengthen muscles that protect joints. Avoid high-impact contact sports like football, boxing, and hockey. A physical therapist can help you choose safe activities.

Take care of your teeth to prevent bleeding gums and lower the need for dental surgery. Tell your dentist you have hemophilia, and plan ahead with your treatment center before any procedure.

Avoid aspirin, ibuprofen, and naproxen unless your hematologist says they are okay. Acetaminophen is usually safer for pain. Get vaccines as shots under the skin instead of into the muscle when possible. Wear a medical alert bracelet and carry a letter about your treatment when you travel.

Hemophilia affects the whole family. Mothers, sisters, and daughters of people with hemophilia may be carriers and can be tested. Genetic counseling can help with family planning. Groups such as the National Bleeding Disorders Foundation and the Hemophilia Federation of America offer education, support, and help with costs.