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Haematocrit (HCT)

(sometimes called, PCV) The proportion of the blood which is made up of red blood cells. The value is given as a percentage of red blood cells in a volume of blood. Normal values are 40-54% in males, 35-47% in females.


A doctor who specialises in diagnosing and treating blood disorders.


The study of blood diseases including leukaemia, lymphoma and myeloma.

Haemopoiesis or haematopoiesis

Term to describe the production and maturation of blood cells from very primitive stem cells. This takes place in the bone marrow which is a spongy tissue in the middle of the bones.

Haemoglobin (HgB, Hb)

​This is the protein in red blood cells which contains iron and carries oxygen around the body. Low haemoglobin levels means the red cells cannot carry out the vital oxygen transport efficiently. Lack of haemoglobin is called anaemia.


Bleeding either to the outside through the skin or internally.

Hairy Cell leukaemia (HCL)

HCL is a rare type of chronic leukaemia related to CLL. It develops slowly from white cells called B lymphocytes. When doctors look at the cells under a microscope, they have hair like outgrowths on their surfaces. It occurs in middle age onwards.


Inflammation of the liver.


Enlargement of the liver.

Herpes zoster

Herpes zoster commonly known as shingles is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body (left or right), often in a stripe. The initial infection with varicella zoster virus (VZV) causes the acute, short-lived illness chickenpox which generally occurs in children and young adults. Once an episode of chickenpox has resolved, the virus is not eliminated from the body and can go on to cause herpes zoster often many years after the initial infection.

Hickman™ line

A kind of central line in which the end of the line is outside the body, unlike a Portacath™. This makes it easier to give chemotherapy.


The investigation of tissue samples by chemical and microscopal analysis.

Hodgkin Lymphoma

was named after the doctor who first recognised it in 1832 – Thomas Hodgkin. Hodgkin lymphomas have a particular appearance under the microscope and they contain cells called Reed Sternberg cells.

Non-Hodgkin lymphomas look different under the microscope and do not contain Reed Sternberg cells.

HLA antigens

A complex family of genetically inherited proteins which are found on the surface of cells throughout the body. They determine the “match” between patient and potential donor in bone marrow transplantation. HLA- factors are inherited from the mother and father and so the greatest chance of having the same HLA-type is between brothers and sisters, i.e. 1 in 4.


Increased levels of calcium in the blood. It is often found in multiple myeloma because the bones are being damaged by the disease. It is dangerous if not controlled.

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