What is hemophilia and bleeding disorders?

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.

When should I call my care team?

Any head injury, even if you feel fine, or a sudden severe headache, vomiting, confusion, or unusual sleepiness; Bleeding that will not stop after your usual treatment; Signs of a joint or muscle bleed: pain, swelling, warmth, or trouble moving a joint; Pain in the groin, hip, or belly, especially with trouble straightening the leg (possible deep muscle bleed); Swelling, tightness, or numbness in an arm or leg; Bleeding in the neck, throat, or mouth that causes trouble swallowing or breathing; Black, sticky stools, or blood in your vomit or urine; Heavy bleeding after childbirth or very heavy periods in a carrier; Hives, swelling of the face or lips, or trouble breathing after a treatment; Leg swelling with pain, or sudden shortness of breath or chest pain while on a rebalancing medicine; If it feels very bad, call 911.

Hemophilia and bleeding disorders

Hemophilia is an inherited condition where blood does not clot well, and today's treatments let most people prevent bleeds and lead active, full lives.

Hi, I'm Rosa. Today we'll go through hemophilia and other bleeding disorders together, one step at a time. I'll keep it simple, and you can pause me, go back, or skip ahead whenever you like. Just so you know, this is for learning only. It is not medical advice, so please check everything with your own doctor and care team. Okay, let's get started.

What hemophilia is

Let's start with the basics. Hemophilia is a condition where blood does not clot well. Clotting is how your body stops bleeding. It needs proteins in the blood called clotting factors. In hemophilia, one factor is missing or too low. People with hemophilia do not bleed faster. They bleed longer. Bleeding often happens inside joints, like knees and ankles. Hemophilia usually runs in families. It mostly affects boys and men. It is not cancer, and it is not catching. Treatment has changed a great deal.

Types of bleeding disorders

Let's talk briefly about the types. Hemophilia A means low clotting factor eight. It is the most common type. Hemophilia B means low clotting factor nine. The signs look the same. Women and girls can carry the gene. Some of them bleed more than usual too. Von Willebrand disease is the most common inherited bleeding disorder. It affects both men and women. Some people make antibodies that block the factor they are given. These are called inhibitors. Your care team will tell you which type you have.

Tests you may have

Now let's talk about tests. Your team will ask about bleeding in your family. Screening blood tests measure how long blood takes to clot. Factor level tests measure how much clotting factor you have. This confirms the diagnosis. It also shows how serious it is. Other blood tests check for von Willebrand disease. A gene test finds the exact gene change. It can help family members too. Regular blood tests check for inhibitors. Joint exams and scans can find joint damage early. You can read more about each test in the guide.

How serious it is

Next up, let's talk about how serious it is. Doctors group hemophilia by your factor level. The lower the level, the more likely bleeding is. There are three groups: severe, moderate, and mild. In severe hemophilia, bleeds can happen with no injury. In mild hemophilia, bleeds mostly happen with surgery or a big injury. Why does this matter? It helps your team plan the right treatment. It also helps everyone speak the same language. Severity usually stays the same for life.

Lab tests to know

Before we move to treatment, there are some things to know. A few lab results guide your treatment plan. There are different tests. Each one has a different role. One shows your natural factor level. One shows how strong an inhibitor is. Some medicines can make certain lab tests look normal when they are not. So always tell every lab that you take them. Your doctor will tell you which results matter for you. Ask them to write down your type and factor level. Keep it with you. The Questions to ask page can help too.

Main treatments

Now let's talk about treatment. Special hemophilia treatment centers have a whole team to help you. Ask to be connected to one. Many people take regular treatment to prevent bleeds. Factor replacement gives the missing factor through a vein. Many people learn to give it at home. Some newer factors last longer, so you need fewer doses. There are shots under the skin that help prevent bleeds. Gene therapy is a one-time treatment for some adults. There are also clinical trials. These are research studies that may offer new options. Ask your team if one fits you.

Side effects and what helps

Let's talk about side effects. The main problem with factor is inhibitors. A sign is bleeding that does not stop as expected. Regular blood tests find them early. Rarely, factor can cause an allergic reaction. Get help right away for trouble breathing. Shots under the skin can cause redness or soreness. Changing the spot each time helps. Some newer medicines can raise the risk of blood clots. Follow your lab checks closely. We have a whole side effects guide on this site.

Living well

Last, let's talk about living well. Many people with hemophilia have few or no bleeds today. Know your bleeding plan, and treat early. Swimming, biking, and walking are good choices. Take care of your teeth. Avoid aspirin and ibuprofen unless your doctor says okay. Wear a medical alert bracelet. Support groups can help the whole family. Now, some signs mean call your team right away. Any head injury, even if you feel fine. Bleeding that will not stop after your usual treatment. Signs of a joint or muscle bleed. If it feels very bad, call 911. Check out our new Screening, prevention and survivorship section.

You did great today. That was a lot to learn, and you went step by step. Write down your questions and bring them to your next visit. Call your care team any time something worries you. You are not alone in this.

Call your care team right away if you have

Any head injury, even if you feel fine, or a sudden severe headache, vomiting, confusion, or unusual sleepiness
Bleeding that will not stop after your usual treatment
Signs of a joint or muscle bleed: pain, swelling, warmth, or trouble moving a joint
Pain in the groin, hip, or belly, especially with trouble straightening the leg (possible deep muscle bleed)
Swelling, tightness, or numbness in an arm or leg
Bleeding in the neck, throat, or mouth that causes trouble swallowing or breathing
Black, sticky stools, or blood in your vomit or urine
Heavy bleeding after childbirth or very heavy periods in a carrier
Hives, swelling of the face or lips, or trouble breathing after a treatment
Leg swelling with pain, or sudden shortness of breath or chest pain while on a rebalancing medicine
If it feels very bad, call 911.

Side effects: what helps

Sources

Quick answers

What is hemophilia and bleeding disorders?: 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.
When should I call my care team?: Any head injury, even if you feel fine, or a sudden severe headache, vomiting, confusion, or unusual sleepiness; Bleeding that will not stop after your usual treatment; Signs of a joint or muscle bleed: pain, swelling, warmth, or trouble moving a joint; Pain in the groin, hip, or belly, especially with trouble straightening the leg (possible deep muscle bleed); Swelling, tightness, or numbness in an arm or leg; Bleeding in the neck, throat, or mouth that causes trouble swallowing or breathing; Black, sticky stools, or blood in your vomit or urine; Heavy bleeding after childbirth or very heavy periods in a carrier; Hives, swelling of the face or lips, or trouble breathing after a treatment; Leg swelling with pain, or sudden shortness of breath or chest pain while on a rebalancing medicine; If it feels very bad, call 911.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.