Information for members of the public

The information within this section of the website is intended for members of the general public in the UK. Here you will find general information about haemophilia B, a condition present from birth which affects the ability of the blood to clot.1

What is haemophilia B?

Haemophilia B is a condition present from birth which affects the ability of the blood to clot. It means that you do not have enough of a protein called clotting factor IX (factor nine) in your blood.1

Haemophilia B has 3 levels of severity – mild, moderate and severe.1

Having haemophilia B means you are more likely to bleed from an injury (through falling, or taking a hard knock for example), but bleeding can also happen for no apparent reason.1

Bleeding often happens inside the body, where you can’t see it (in places like the knees, ankles and elbows)1.

If you sustain an injury externally, it may mean excessive bleeding.1

There is no cure for haemophilia B, but with the right care, people with the condition can still lead a full and active life.

Further information and support can be found via The Haemophilia Society, a UK-wide charity for all those affected by bleeding disorders.

If you are a patient / carer of a patient who has already been prescribed Idelvion in the UK, you can get more information by clicking here.

Reporting side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet.You can also report side effects directly via the Yellow Card Scheme at By reporting side effects you can help provide more information on the safety of this medicine.