In hemophilia A, Factor VIII is either
missing or not working properly

When an injury causes a bleed, a process called hemostasis occurs at the injury site to form a clot and stop the bleed

Hemostasis is achieved in 2 parts:

  • Primary hemostasis: Platelets are recruited to the site of the injury and, with the help of von Willebrand Factor (vWF), create a “platelet plug” to reduce blood loss
  • Secondary hemostasis: This is where the multistep clotting cascade is activated to form a fibrin mesh around the platelets to stabilize the clot

Without enough Factor VIII, your body’s ability to generate thrombin is reduced, meaning:

Blood cannot clot properly

Blood clot unable to form

Excessive bleeding can occur

Icon of two red blood drops
Restoring hemostasis is essential for stable clot formation
What are factor activity levels?

The amount of Factor VIII in your blood is called your “factor activity level”

Everyone’s factor activity levels are different. People with lower factor levels have greater bleed risk, and people with higher factor activity levels have better protection. Every person has unique treatment goals. That’s why it’s important to talk to your doctor about managing your hemophilia.

Keeping factor levels up with prophylaxis treatment will help provide better protection against bleeds

Factor levels can impact lifestyle and activity

The more factor you have in your body, the better your bleed protection is, which is why many people with hemophilia choose prophylaxis treatment.

General guidelines on Factor VIII levels and their impact on the ability to perform activities
Factor VIII Levels
Impact on Physical Activity/Lifestyle
Normal levels50%-150% factor activity
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May be able to engage in higher-impact activity without pain
(sports, physical jobs, and active days)
Near-normal*≥40%‑<50% factor activity
Near-normal factor activity levels are currently undefined
by the World Federation of Hemophilia
Mild hemophilia5%‑<40% factor activity
1%-5% factor
Icon of a golf green and flagpole
May engage in limited activity with some pain (walking, golfing,
sailing, gardening), with a risk of spontaneous bleeds or microbleeds
  • Requires minor adjustments in lifestyle and the physical activity level can be mild and moderate
  • Supplemental factor is needed for surgery
Severe hemophilia<1% factor activity
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A person’s lifestyle is considered “vulnerable,” which means their level of physical activity is low to sedentary
  • There is a high risk of spontaneous bleeds and pain with target joints
  • Supplemental factor is needed for surgery

*WFH Guidelines define the upper limit of mild hemophilia as 40% factor activity and the WFH Introduction to Hemophilia defines the normal range as 50% to 150%, which indicates that 40% to 50% would be in between mild hemophilia and normal, here referred to as “near-normal” levels.

WFH=World Federation of Hemophilia.

People with hemophilia take prophylaxis treatments, or preventative treatments, to help keep their factor levels higher to reduce the risk of a bleed

For people treating on-demand, treatment increases their factor levels and restores hemostasis after a bleed occurs.

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Sanofi Hemophilia Community Relations and Education (CoRe) Managers offer education to people living with hemophilia and their families. CoRe Managers provide information about living with hemophilia and treatment options. Use our handy CoRe Locator to find the CoRe team member nearest you.

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