A Patient’s Guide to Managing Haemophilia A and B

Hemophilia is an inherited condition in which the blood does not clot properly, so bleeding goes on longer than it should, most often into joints and muscles rather than from cuts [1].

This page provides general information. It does not replace advice from a doctor or another qualified healthcare professional.

Key facts

Hemophilia A is caused by too little clotting factor VIII, and hemophilia B by too little factor IX. They cause the same problems and are told apart by blood tests [1,3].
Hemophilia A affects about 1 in 4,000 to 1 in 5,000 male babies, and hemophilia B about 1 in 20,000 [2].
It mostly affects males, and about a third of people are the first in their family to have it [1].
Females who inherit a changed copy of the gene can have low factor levels and real bleeding, and are increasingly described as having hemophilia rather than merely carrying it [4,6].
The main long-term problem is bleeding into joints, which over time damages them [4,6].
There is no cure, though regular preventive treatment now allows most people with good access to care a near-normal life expectancy [4,6].

What is hemophilia?

Hemophilia is an inherited condition in which the blood does not clot properly, so bleeding goes on longer than it should [1].

When a blood vessel is damaged, small cells called platelets stick to the spot, then a chain of proteins called clotting factors builds a mesh that holds the plug in place [2]. If one factor is missing, the chain stops partway and the clot stays fragile.

Hemophilia A is caused by too little clotting factor VIII, and hemophilia B by too little factor IX [1,3]. Hemophilia A is also called classic hemophilia, and hemophilia B Christmas disease [1,2]. The two behave almost identically, so a blood test measuring each factor is used to tell them apart, which is practical rather than academic, since the medicines differ [3,5]. Acquired hemophilia is a separate, non-inherited condition that starts later in life and affects men and women equally [2,10].

How common is it?

Hemophilia is rare. Hemophilia A is present in about 1 in 4,000 to 1 in 5,000 male babies worldwide, and hemophilia B in about 1 in 20,000 [2]. Hemophilia A is roughly three to four times as common [1].

Using prevalence rates from national patient records in six high-income countries, the World Federation of Hemophilia expects around 850,000 people worldwide to have hemophilia, about 289,000 of them the severe form [7,8]. Its 2024 survey of 135 countries found only 271,918 people known to have hemophilia [8]. More than 75 percent of those expected have not been identified and diagnosed, and identification varies by region, from about 85 percent of the expected number in Europe to about 8 percent in Africa [8,9].

What causes it?

Genes are the instructions inside our cells. A change in the F8 gene, which holds the instructions for factor VIII, causes hemophilia A. A change in the F9 gene, which does the same for factor IX, causes hemophilia B [2].

Both genes sit on the X chromosome, one of the two chromosomes linked to sex, so the pattern is called X-linked inheritance. Males have one X chromosome and so one copy, which means a single changed copy causes hemophilia. Females have two, and the second copy can often make up the shortfall [1,2]. About 30 percent of males with hemophilia A are the first in their family to have it [4].

Females can have hemophilia, not only carry it. Older material calls any female with a changed copy a “carrier”, which implies she is unaffected. That is frequently wrong. One X chromosome in each cell is switched off at random early in life, and if the working copy is switched off in most cells, factor levels fall [2]. Around 30 percent of females with one changed F8 copy have factor VIII below 40 percent, low enough to cause bleeding, and about 25 percent of those with normal levels still report abnormal bleeding [4]. Current practice is to describe such a woman as having mild, moderate or severe hemophilia and to treat her the same way, and 2026 guidance says the impact on women and girls is still insufficiently recognized [4,6,12].

What are the symptoms?

People with hemophilia bleed for longer than other people, and the bleeding that causes most trouble is inside the body rather than from cuts [10]. Severity depends on how much clotting factor is present [6]:

Severe, below 1 percent of normal: bleeding into joints and muscles with no injury at all, usually found in the first year or two [4,6].
Moderate, 1 to 5 percent: occasional bleeding without injury, and long bleeding after minor injury or surgery [4,6].
Mild, 5 to under 40 percent: rarely bleeds without injury, with heavy bleeding after major injury, surgery or dental work [4,6].

Common signs are swelling and pain in a joint, bleeding into muscle, long bleeding after dental work or surgery, nosebleeds, and blood in urine or stool [1]. Heavy periods are a common sign in girls and women [4]. Joints account for roughly 70 to 80 percent of bleeds, most often knees, elbows and ankles [6]. Repeated bleeding into a joint inflames its lining and in time wears away cartilage and bone, the main long-term problem and the main cause of lasting disability [4,6].

When to seek urgent help. Call emergency services for a head injury, a serious injury, blood in the stool, vomiting or coughing up blood, or a sudden severe headache with confusion [3]. Give the usual clotting treatment first if it is to hand [3]. Guidelines say treatment for suspected bleeding in or around the brain must be given immediately, before any scan [6]. Contact the hemophilia team the same day for pain or swelling in a joint [3].

How is it diagnosed?

Diagnosis usually starts with a family doctor or a pediatrician, who refers on to a hemophilia center [3]. Where hemophilia is already in the family, testing can be arranged soon after birth [1].

Clotting tests come first. The platelet count and the prothrombin time are normal, while a test called the activated partial thromboplastin time is prolonged [4]. Factor assays, blood tests that measure factor VIII and factor IX activity, then give both the type and the severity [1]. In mild hemophilia A the standard test can read close to normal, so a different method is sometimes needed [4].

Genetic testing of F8 or F9 confirms the diagnosis and lets relatives be tested [4]. Guidance recommends that all mothers, sisters and daughters of a person with hemophilia have their factor levels measured, especially before surgery or pregnancy [6].

How is it treated?

There is no cure, though treatment has changed enormously and is still changing [3].

Preventive treatment rather than treating each bleed. On-demand treatment means treating each bleed as it happens. Prophylaxis means treating regularly so bleeds do not happen, and it is the standard of care for anyone with a severe bleeding pattern, ideally started before age three, since on-demand treatment does not prevent joint damage [6]. Access differs sharply between countries, and the World Federation of Hemophilia recommends prophylaxis everywhere, at lower doses where access is limited [6].

Factor replacement. Concentrates of factor VIII or factor IX are given into a vein, often at home. Newer products such as efanesoctocog alfa, FDA-approved for hemophilia A in February 2023, last longer and need fewer infusions [1,4,13].

Treatments that are not factor. Emicizumab is an antibody that does the job factor VIII normally does. Given by injection under the skin, it transformed hemophilia A care, and was authorized in the EU in February 2018 for use with or without inhibitors [4,6,14]. Rebalancing treatments ease off the body’s natural brakes on clotting instead of replacing the missing factor. Three are approved for both types: marstacimab and concizumab (EU, November and December 2024) and fitusiran (FDA, March 2025) [15,16,17]. The trade-off is a risk of unwanted clots [18].

Gene therapy. Gene therapy delivers a working copy of the gene to liver cells in a single infusion. Valoctocogene roxaparvovec was approved for hemophilia A by the FDA in June 2023, and etranacogene dezaparvovec for hemophilia B in the EU in February 2023 [19,20]. Five-year results showed factor IX holding steady after hemophilia B gene therapy, while factor VIII fell over time after hemophilia A gene therapy, with 25 of 134 participants returning to preventive treatment [21,22]. A second hemophilia B product was discontinued in 2025, and in February 2026 the World Federation of Hemophilia reported that the hemophilia A product is being withdrawn [23,24]. Cost is very high, in England access is restricted, and a second dose is not possible [25,26].

Inhibitors. An inhibitor is an antibody that blocks infused factor and makes bleeds much harder to treat. It is the most serious complication. About 30 percent of people with severe hemophilia A develop one, against up to 5 percent in hemophilia B [6]. Immune tolerance induction, repeated doses of factor to retrain the immune system, succeeds in 70 to 80 percent of severe hemophilia A [6]. Emicizumab and the rebalancing treatments protect against bleeding whatever the inhibitor status [27].

Living with hemophilia

Care works best through a hemophilia treatment center, where hematology, nursing, physical therapy, laboratory work and psychological support sit together, and people followed at one have lower mortality [4,6]. Physical therapy is central rather than optional, alongside regular treatment, to keep muscles and joints working [6]. Activity is encouraged: swimming, walking, cycling and golf are recommended, while contact sports are advised against unless preventive treatment covers them [6]. Dental care is a priority, since gum disease causes bleeding [6]. Check new medicines with the hemophilia team, avoid aspirin and anti-inflammatory painkillers, and consider a medical alert bracelet [3]. With modern treatment, life expectancy is approaching that of the general population [4].

The infected blood years. Clotting factor made from donated plasma in the late 1970s and 1980s carried viruses. Many people who received it between 1979 and 1985 contracted HIV, about half of whom died of AIDS before effective treatment existed, and most people exposed before the late 1980s became chronically infected with hepatitis C [4]. The UK Infected Blood Inquiry reported in May 2024 that around 1,250 people with bleeding disorders in the UK were infected with HIV, three quarters of whom have died, and that this could largely have been avoided [28]. A UK compensation scheme has since been set up [29]. Viral inactivation and donor screening ended HIV transmission from 1985 and hepatitis B and C from 1990 [4].

Thinking about a clinical trial?

Clinical trials are research studies that test whether a treatment works and is safe. Hemophilia is an active research area, so studies come up fairly often. Deciding whether to look into one is personal, and it helps to take it in steps.

1. Understand what the study is asking

It is worth being clear on what a study actually involves:

what the researchers are trying to learn
what treatment is being studied, and what it is being compared with
how long the study lasts, which for gene therapy studies can be many years
what visits, tests or procedures are involved, and how often
the possible benefits, and the known and unknown risks

2. Consider possible medical suitability

Every trial has rules about who can take part. These are called eligibility criteria. Some describe who can join, and others who cannot. For a hemophilia study they might include a confirmed diagnosis with a factor level below a set figure, whether it is hemophilia A or B, whether a person has ever had an inhibitor, the number of bleeds in the past year, an age range, current treatment, liver health, and for gene therapy whether the body already carries antibodies to the delivery vehicle.

trialport’s medifit helps people consider information related to possible medical suitability. It does not diagnose a condition, confirm eligibility or replace formal screening by the study team.

Explore hemophilia clinical trials through trialport

3. Consider whether participation fits your life

Medical suitability is only part of the picture. A study can look right on paper and still be hard in practice. Worth thinking through:

the time each visit takes, and how many there are
travel, distance and who would come along
work, school or caring responsibilities
how you feel about infusions, injections or repeated blood tests
whether a long follow-up period fits your plans
whether you understand the study well enough to decide
for parents, how a child feels about it

trialport’s readifit helps people reflect on their understanding, motivation, time, routines, support, emotions and practical arrangements.

4. Ask questions before deciding

Useful questions to put to a research team:

Why is this study being carried out?
What exactly would I need to do, and for how long?
What are the known risks, and what is still unknown?
Could I receive a placebo? A placebo is a dummy treatment with no active medicine, used so researchers can compare results fairly.
Would I keep my usual preventive treatment, and what happens if I have a serious bleed?
How would you monitor me, and what would you do if the treatment stopped working?
Can I leave the study after joining, and are travel costs covered?
What happens after the study ends, and will I be told the results?

Taking part is voluntary. A person can ask questions, speak with people they trust and choose not to participate.

Search for clinical trials at app.trialport.com.

Current research

Research covers several areas:

How long gene therapy lasts. Follow-up published in 2026 shows factor IX staying steady five years after hemophilia B gene therapy, while factor VIII declines after hemophilia A [21,22].
Next-generation gene therapy. Gene editing, different delivery vehicles and ways to allow a second dose are under study. None is approved [26,30].
Rebalancing treatments in everyday use. Attention has moved to combining them safely with factor treatment for breakthrough bleeds and surgery [18].
Women and girls. Under-representation in research is now acknowledged, and 2026 brought formal guidance on diagnosing hemophilia in women and girls [12,31].

Study status checked: 3 August 2026. Research moves and what is being studied changes, so this list will date. For current information, search at app.trialport.com.

Support and further information

Internationally, the World Federation of Hemophilia publishes the main treatment guidelines and works through member organizations in more than 150 countries, the best starting point outside the US and UK [6,8]. In the United States, the National Bleeding Disorders Foundation publishes plain-language information and treatment news [23]. In the United Kingdom, The Haemophilia Society offers booklets, a helpline and its Talking Red work for women and girls [10,11], and the NHS guide to haemophilia sets out when to seek urgent help [3]. Coverage is thinner across much of Africa, South Asia and South America [8,9].

Well-known people with hemophilia

Ryan White (1971 to 1990) was an American teenager with severe hemophilia A who contracted HIV from contaminated factor VIII concentrate. The US Ryan White HIV/AIDS Program is named after him [32,33].
Alex Dowsett is a British professional cyclist with severe hemophilia A who founded Little Bleeders, a charity for young people with bleeding disorders [34].
Chris Bombardier has severe hemophilia B and in 2017 became the first person with hemophilia to summit Everest [35].
Alexei Nikolaevich Romanov, the Russian tsarevich, had the condition long known as the royal disease. Analysis of the Romanov remains in 2009 confirmed it as hemophilia B [36].

Questions people often ask

What is the difference between hemophilia A and B?
Hemophilia A is a shortage of factor VIII and hemophilia B a shortage of factor IX. Symptoms are the same, so only a blood test tells them apart, and the medicines differ [1,3].

Can women and girls have hemophilia?
Yes. Around 30 percent of females with a changed F8 copy have factor VIII below 40 percent, low enough to cause bleeding, and current practice is to describe them as having hemophilia rather than carrying it [4,6].

Is there a cure?
No. Treatment can prevent most bleeding, and gene therapy can reduce the need for infusions for a time, though how long that lasts is not yet clear [3,21,22].

Will my children inherit it?
A father passes the changed gene to all of his daughters and none of his sons. A mother with one changed copy has a 1 in 2 chance in each pregnancy [2,4].

Is hemophilia the same as von Willebrand disease?
No. Von Willebrand disease is far more common, affects men and women equally, and usually causes bleeding from the skin and linings rather than into joints [1,3].

Is clotting treatment safe now?
Yes. Products used today are made in a laboratory or virally inactivated, and HIV transmission ended in 1985, hepatitis B and C in 1990 [3,4].

Sources

Centers for Disease Control and Prevention. About Hemophilia. Last reviewed 5 March 2025. https://www.cdc.gov/hemophilia/about/index.html Accessed 3 August 2026.
MedlinePlus Genetics, National Library of Medicine. Hemophilia. https://medlineplus.gov/genetics/condition/hemophilia/ Accessed 3 August 2026.
National Health Service (United Kingdom). Haemophilia. Page last reviewed 9 January 2025. https://www.nhs.uk/conditions/haemophilia/ Accessed 3 August 2026.
Konkle BA, Nakaya Fletcher S. Hemophilia A. In: Adam MP, et al, editors. GeneReviews. Seattle: University of Washington; last update 7 August 2025. https://www.ncbi.nlm.nih.gov/books/NBK1404/ (PMID 20301578). Accessed 3 August 2026.
Konkle BA, Nakaya Fletcher S. Hemophilia B. In: Adam MP, et al, editors. GeneReviews. Seattle: University of Washington; last update 7 August 2025. https://www.ncbi.nlm.nih.gov/books/NBK1495/ (PMID 20301668). Accessed 3 August 2026.
Srivastava A, Santagostino E, Dougall A, et al. WFH Guidelines for the Management of Hemophilia, 3rd edition. Haemophilia. 2020;26(Suppl 6):1-158. doi:10.1111/hae.14046. https://haemophilia.org.uk/wp-content/uploads/2020/12/WFH-Guidelines-for-the-Management-of-Hemophilia-3rd-edition.pdf Accessed 3 August 2026.
Iorio A, Stonebraker JS, Chambost H, et al. Establishing the Prevalence and Prevalence at Birth of Hemophilia in Males: A Meta-analytic Approach Using National Registries. Annals of Internal Medicine. 2019;171(8):540-546. doi:10.7326/M19-1208. https://europepmc.org/article/MED/31499529 (PMID 31499529). Accessed 3 August 2026.
World Federation of Hemophilia. Report on the Annual Global Survey 2024. Montreal: WFH; October 2025. https://www1.wfh.org/publications/files/pdf-2588.pdf Accessed 3 August 2026.
World Federation of Hemophilia. Identification and Diagnosis. https://wfh.org/identification-and-diagnosis/ Accessed 3 August 2026.
The Haemophilia Society (United Kingdom). Haemophilia. Last updated 10 February 2026. https://haemophilia.org.uk/bleeding-disorders/haemophilia-a-and-b/ Accessed 3 August 2026.
The Haemophilia Society (United Kingdom). Women with Bleeding Disorders. https://haemophilia.org.uk/bleeding-disorders/women-with-bleeding-disorders/ Accessed 3 August 2026.
Srivaths L, Ardila J, Fijnvandraat K, et al. The diagnosis and evaluation of women and girls with hemophilia and hemophilia carriers: guidance from the SSC of the ISTH. Journal of Thrombosis and Haemostasis. 2026. doi:10.1016/j.jtha.2026.06.022 (PMID 42362028). https://europepmc.org/article/MED/42362028 Accessed 3 August 2026.
US Food and Drug Administration. ALTUVIIIO (efanesoctocog alfa). https://www.fda.gov/vaccines-blood-biologics/altuviiio Accessed 3 August 2026.
European Medicines Agency. Hemlibra (emicizumab), medicine overview and product information. https://www.ema.europa.eu/en/medicines/human/EPAR/hemlibra Accessed 3 August 2026.
European Medicines Agency. Hympavzi (marstacimab), medicine overview and product information. https://www.ema.europa.eu/en/medicines/human/EPAR/hympavzi Accessed 3 August 2026.
European Medicines Agency. Alhemo (concizumab), medicine overview and product information. https://www.ema.europa.eu/en/medicines/human/EPAR/alhemo Accessed 3 August 2026.
US Food and Drug Administration. FDA Approves Novel Treatment for Hemophilia A or B, with or without Factor Inhibitors. Press announcement, 28 March 2025. https://www.fda.gov/news-events/press-announcements/fda-approves-novel-treatment-hemophilia-or-b-or-without-factor-inhibitors Accessed 3 August 2026.
Nakajima Y, Nogami K. Non-factor Therapies in Hemophilia: Mechanisms, Clinical Evidence, Patient Management, and Future Perspectives. Advances in Therapy. 2026;43. doi:10.1007/s12325-026-03583-7 (PMID 41954861). https://europepmc.org/article/MED/41954861 Accessed 3 August 2026.
US Food and Drug Administration. ROCTAVIAN (valoctocogene roxaparvovec-rvox). https://www.fda.gov/vaccines-blood-biologics/roctavian Accessed 3 August 2026.
European Medicines Agency. Hemgenix (etranacogene dezaparvovec), medicine overview and product information. https://www.ema.europa.eu/en/medicines/human/EPAR/hemgenix Accessed 3 August 2026.
Leavitt AD, Mahlangu J, Raheja P, et al. Durability of efficacy, safety, and quality of life 5 years after valoctocogene roxaparvovec gene transfer for severe hemophilia A: final phase 3 GENEr8-1 trial results. Research and Practice in Thrombosis and Haemostasis. 2026;10(3):103416. doi:10.1016/j.rpth.2026.103416 (PMID 42064204). https://europepmc.org/article/MED/42064204 Accessed 3 August 2026.
Pipe SW, Miesbach W, Recht M, et al. Final Analysis of a Study of Etranacogene Dezaparvovec for Hemophilia B. New England Journal of Medicine. 2026;394. doi:10.1056/NEJMoa2514332 (PMID 41358585). https://europepmc.org/article/MED/41358585 Accessed 3 August 2026.
National Bleeding Disorders Foundation. Pfizer Discontinues Beqvez Hemophilia B Gene Therapy. 25 February 2025. https://www.bleeding.org/news/pfizer-discontinues-beqvez-hemophilia-b-gene-therapy Accessed 3 August 2026.
World Federation of Hemophilia. WFH statement on discontinuation of valoctocogene roxaparvovec-rvox (ROCTAVIAN). 25 February 2026. https://wfh.org/article/wfh-statement-on-discontinuation-of-valoctocogene-roxaparvovec-rvox-roctavian/ Accessed 3 August 2026.
National Institute for Health and Care Excellence. Etranacogene dezaparvovec for treating moderately severe or severe haemophilia B. Technology appraisal guidance TA989. 24 July 2024. https://www.nice.org.uk/guidance/ta989/chapter/1-Recommendation Accessed 3 August 2026.
Miesbach W, Herzog RW. Six-year FIX-Padua gene therapy in hemophilia B. Blood Advances. 2026;10(10):3715-3716. doi:10.1182/bloodadvances.2026020150 (PMID 42139099). https://europepmc.org/article/MED/42139099 Accessed 3 August 2026.
Escuriola Ettingshausen C. Update: Immune Tolerance Induction Practice in Haemophilia. Hämostaseologie. 2026. doi:10.1055/a-2887-8098 (PMID 42409069). https://europepmc.org/article/MED/42409069 Accessed 3 August 2026.
Infected Blood Inquiry. The Report, Volume 1: Overview and Recommendations. HC 569-I. London: 20 May 2024. https://www.infectedbloodinquiry.org.uk/reports/inquiry-report Accessed 3 August 2026.
Infected Blood Compensation Authority (United Kingdom). About us. https://www.gov.uk/government/organisations/infected-blood-compensation-authority Accessed 3 August 2026.
Kumarasamy N, Balakrishnan B. Exploring gene editing as a potential therapeutic strategy for hemophilia. Frontiers in Bioengineering and Biotechnology. 2026;14:1727204. doi:10.3389/fbioe.2026.1727204 (PMID 41716627). https://europepmc.org/article/MED/41716627 Accessed 3 August 2026.
Uminski K, Cusano E. The XX Factor in Hemophilia: Diagnostic, Therapeutic, and Research Gaps for Women and Girls. Haemophilia. 2026. doi:10.1111/hae.70366 (PMID 42533850). https://europepmc.org/article/MED/42533850 Accessed 3 August 2026.
Health Resources and Services Administration, US Department of Health and Human Services. Who Was Ryan White? https://ryanwhite.hrsa.gov/about/ryan-white Accessed 3 August 2026.
Martini M, Orsini D. In memory of Ryan White, the boy with haemophilia who showed the world the other side of AIDS. Journal of Preventive Medicine and Hygiene. 2025;66(4):E643-E648. doi:10.15167/2421-4248/jpmh2025.66.4.3819 (PMID 42256476). https://europepmc.org/article/MED/42256476 Accessed 3 August 2026.
The Haemophilia Society (United Kingdom). Little Bleeders. https://haemophilia.org.uk/little-bleeders/ Accessed 3 August 2026.
HemAware, National Bleeding Disorders Foundation. Chris Bombardier: Reaching New Heights. https://hemaware.org/mind-body/chris-bombardier-reaching-new-heights Accessed 3 August 2026.
Rogaev EI, Grigorenko AP, Faskhutdinova G, Kittler ELW, Moliaka YK. Genotype analysis identifies the cause of the “royal disease”. Science. 2009;326(5954):817. doi:10.1126/science.1180660 (PMID 19815722). https://europepmc.org/article/MED/19815722 Accessed 3 August 2026.

Review information

Written by: trialport editorial team
Reviewed by: Keith Berelowitz, Founder and CEO, trialport
Reviewed on: 3 August 2026
Next review due: 3 August 2027
References last checked: 3 August 2026

Hemophilia A and B: a plain-language guide