About haemophilia in females

Can females have haemophilia?

Many girls or women who have the factor VIII (8) or IX (9) gene alteration causing haemophilia 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.

In genetics any female who has this gene alteration is called a 'haemophilia carrrier'.

However, approximately 20-30% of girls and women who are carriers have reduced clotting factor levels and may have a bleeding tendency.

In the past women and girls with bleeding symptoms were generally 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 females with factor levels at the lower end of normal (40-50%) may also experience abnormal bleeding. If further investigation shows that this bleeding is related to a factor VIII or IX deficiency, they will be treated as having haemophilia, but they will be described as a 'symptomatic haemophilia carrier'.

Factor level testing

All females who are carriers 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 are carriers 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 gene alteration causing haemophilia. Many females who carry the gene alteration 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 alteration.

Click here for more information on genetic testing

Read the booklet:
Haemophilia testing in women and girls
Haemophilia testing in women and girls: your questions answered (genetic testing and factor level 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: June 2022