1-month supply

The amount of medicine you use during a 1-month period. In most cases, your doctor will prescribe a 1-month supply or less for short-term medicine.



A protein made by the body’s immune system to fight and destroy foreign substances, such as viruses, not normally found in the body. In some people with hemophilia, the immune system may make an antibody in response to infused clotting factor proteins. This is called an inhibitor.


Joint disease. Repeated bleeding into the joints of a person with hemophilia may cause arthropathy.


A laboratory test that measures the amount of clotting factor activity. In the manufacture of clotting factor concentrates, assay is indicated on each vial of product to indicate the number of clotting factor units (listed as i.u., or international units).


Bleeding episode (bleed)

A collection of blood at a site inside or on the surface of the body that occurs when a person with a bleeding disorder is actively bleeding.

Blood vessel

The part of the body that carries blood to and from all body areas. An artery carries oxygen-rich blood from the heart to the body’s tissues; a vein carries blood from the body’s tissues back to the heart and lungs to receive more oxygen. Capillaries are the small blood vessels that get oxygen into the tissues and connect veins and arteries.

Butterfly needle

A type of needle used to infuse factor or other medications into a vein. It has a small metal needle connected to plastic tubing and wings used to hold the needle during insertion. These are single-use items that must be disposed of in a puncture-resistant container after use.



Long-lasting or lifelong.


A jelly-like substance made of a protein called fibrin interacting with blood cells called platelets. A clot forms to stop bleeding from a damaged blood vessel.


The process by which liquid blood changes into a jelly-like substance to seal an injured blood vessel and stop bleeding.


Factor concentrate

A freeze-dried powder product that contains measured amounts of a particular clotting factor, such as factor VIII or factor IX.

Factor level

The amount of clotting factor in the blood, referred to as a percentage of normal.


Gene therapy

A method of treating or curing hemophilia by replacing the defective gene with normal factor VIII or factor IX genes so the body will produce factor. This is currently an experimental process that is being researched. Studies are currently underway for both hemophilia A and hemophilia B.



The amount of time it takes the body to use up one-half of the factor level circulating in the blood. Factor VIII concentrates have a half-life of approximately 8 to 12 hours. Extended half-life factor VIII products range from 12 to 20 hours. Factor IX concentrates have a half-life of approximately 18 to 24 hours. Extended half-life factor IX products range from 66 to 118 hours.


See “joint bleed”

Hemophilia treatment center (HTC)

A specialized treatment facility where a team of healthcare providers (hematologists, nurses, social workers, physical therapists, and other disciplines) work together to deliver comprehensive care for people with bleeding disorders and their families.

Home therapy

Administration of treatment products in the home by a nurse, the caregiver or the patient.


Immune tolerance induction (ITI)

Treatment used to overcome an inhibitor that may require high daily doses of clotting factor for an extended period of time with a goal of suppressing inhibitors.


The body’s defensive reaction to injury or irritation. Symptoms include swelling, heat, redness, and pain. In people with hemophilia, inflammation may occur in response to a bleeding episode.


Giving a medication or solution into a vein. In hemophilia, infusion refers to giving factor into a vein or central venous access device.


A protein produced by the body that attaches to the factor VIII and neutralizes it, so the infused factor does not work to stop a bleed in hemophilia A, or binds to factor IX and produces an allergic, often anaphylactic-type reaction in hemophilia B. The body produces this protein or antibody when the immune system recognizes infused factor as foreign protein and prevents it from working.



A place in the body where two or more bones come together.

Joint bleed

When a bleed occurs in a joint. Also called hemarthrosis.



Liquid portion of the blood that contains clotting proteins.


Disc-shaped blood cells that initially plug an injury to a blood vessel.


A type of central venous access device surgically implanted under the skin to allow easy access to a vein for factor infusion. A port is made up of a small reservoir with a rubber-like top. The reservoir is attached to a plastic tube that is inserted into a large vein, usually in the upper chest. A special needle is used to inject factor through the skin into the top of the port. The factor travels through the tube into the vein.



Complementary treatment for bleeding episodes used in addition to factor therapy. The letters stand for rest, ice, compression, and elevation of the injured area.

View Accredo’s RICE guide for more information


Specialty pharmacy

A company that provides factor products and infusion supplies in the home setting to support home treatment of hemophilia. Specialty pharmacies many times have customer service representatives and trained pharmacists and nurses that can assist with bleeding disorder needs. An example of a specialty pharmacy with staff trained in bleeding disorders is Accredo.

Spontaneous bleed

A bleeding episode that occurs with no obvious cause.


Inflammation of the synovium of the joint that may result from joint bleeds. Left untreated, synovitis can lead to joint damage.


The tissue lining a joint that produces a fluid that lubricates the joint. Bleeding into a joint occurs from blood vessels in the synovium.


Target joint

A joint that bleeds repeatedly, at least three times within a 6-month period. Target joints bleed more frequently and often require more doses of factor for bleed resolution than non-target joints.





A measurement of factor activity referring to that found in 1 milliliter of normal plasma. Prescriptions to treat hemophilia are usually written as a target dose number of units based on kilogram of body weight, plus or minus 10% to allow for variances in factor production. Unit of factor concentrates (see Assay) refers to a standardized “international unit” (i.u.) of factor activity per vial of product.



Insertion of a needle directly into a vein.