About haemophilia in females

Can females have haemophilia?

Many girls or women who carry the altered factor VIII (8) or IX (9) gene causing haemophilia (the "haemophilia gene") do not have symptoms of a bleeding disorder. If at least one of their X chromosomes has a factor VIII or IX gene that works, their body can usually produce normal or near normal levels of factor and they do not have bleeding problems.

However, approximately 20-30% of girls and women who carry this gene have reduced clotting factor levels and may have a bleeding tendency. They used to be described as “symptomatic carriers”. If their factor levels fall in the range for mild haemophilia (5 – 40% of normal clotting factor), they are now recognised as having mild haemophilia. In very rare cases, some girls or women have particularly low factor levels causing them to have moderate or severe haemophilia. Some women with factor levels between 40% and 60% of normal also experience abnormal bleeding.

Factor level testing

All females who carry the gene should have testing for their clotting factor levels. Ideally this should be done early in life so that females with low factor levels are identified and managed appropriately before they have problems with bleeding.

Unlike males with haemophilia, where the factor level is nearly always the same within the same family, the factor level in females who carry the gene is unpredictable and varies between family members.

Women and girls with lower levels should have theirs checked periodically, as their factor levels may change with age, pregnancy and hormonal medications. If their factor level is low, they will need a treatment plan to prevent bleeding problems and manage any situations that occur, including medical and dental procedures and surgery.

It is important to remember that normal factor VIII or factor IX levels will not tell you whether you have the altered gene causing haemophilia. Many females who carry the gene have normal factor levels. Finding out your clotting factor level helps you and your Haemophilia Treatment Centre decide if you need to develop a treatment plan specifically for you. If your levels are normal a separate genetic test is needed to find out if you have the gene.

Click here for more information on genetic testing

Download the fact sheets:
Haemophilia A and haemophilia B
Haemophilia in females (PDF, 1.1 MB)

Working with your HTC
Haemophilia treatment and care for young women (PDF 1.3 MB) 

Date last reviewed: March 2021