Glossary of Terms

This glossary of terms is meant to help everyone understand medical words. It is a place to quickly find information on medical words.

To find a word or term begin by clicking on a letter in the A-Z list. Then you can browse down the list to find the word you want. You can also type your medical word in the search box in the upper right corner and then click on the little magnifying glass.

This glossary is for information only. It should never be used instead of advice from a healthcare provider.

If you have questions or comments about the Glossary of Terms please let us know.

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haemophilus influenza

disease is caused by a bacterial infection. The illness can range from mild to severe. It has nothing to do with the influenza virus (flu)



bad breath


see or hear things that are not there

hand hygiene

hand washing


harmful, danger

healthcare provider

a person whose job it is to take care of the health of others

heart attack

when part of your heart can't get enough oxygen and some of your heart tissue dies

heart failure

when your heart can't pump enough blood through your body

heart murmur

an unusual sound heard between heartbeats

extra swishing sound made by the heart when blood goes through it. Some cause no problems and others need to be treated medically or surgically.


an abnormal buildup of blood vessels on or under the surface of the skin

commonly called a "strawberry" or strawberry hemangioma by parents. It is a type of vascular birthmark that typically appear in the first few weeks after a baby is born, can grow rapidly during an infant's first year of life, and then typically goes away by the time the child is 5 to 8 years old.

hematocrit (HCT)

amount of red blood cells in your blood

hematocrit test

blood test that counts your red blood cells


about blood


medical doctor who looks after patients with blood conditions


the study of blood and blood diseases



a solid swelling of clotted blood in your tissues


blood in your urine


using a machine to clean your blood

a treatment for kidney failure that removes wastes and water from your blood

a treatment for kidney failure in which your blood passes through a dialyzer to remove wastes and water

kidney disease causes your kidneys to lose their ability to filter and remove waste and extra fluid from your body. Hemodialysis is a process that uses a man-made membrane (dialyzer) to remove wastes, from your blood.


red blood cells that carry oxygen to body cells


a protein in red blood cells that carries oxygen throughout the body

hemoglobin A1c

a blood test to show your blood sugar levels over the last 3 months


a rare bleeding disorder where the blood doesn’t clot normally. 

hemophilia causes a person to bleed a lot, even from a small cut.

a rare inherited bleeding disorder with no known cure. People with hemophilia bleed longer than others. The bleeding can occur in the joints or muscles of the body or on the skin from minor cuts or trauma.


condition where the veins around your anus become swollen and may bleed or cause pain


about your liver

hepatitis A

liver disease

liver disease that you get from drinking bad water or eating bad food

hepatitis B

liver disease you get from someone else's blood or body fluids

hepatitis C

liver disease that you get from someone else's infected body fluids, such as blood or semen

hepatitis D

virus that can only be found in your blood if you also have hepatitis B


when a part of the body (from the inside) pushes through a weak spot in the muscle or surrounding tissue

protrusion of an organ through a tissue that normally contains the organ

herpes simplex

virus, sores, cold sores

herpes simplex virus, also known as HSV, is an infection that causes herpes. Herpes can appear in various parts of the body, most commonly on the genitals or mouth

herpes zoster (shingles)

a condition that causes painful sores on your skin

an infection that shows up as a painful skin rash with blisters, usually on part of one side of the body (left or right), often in a strip

high risk

a good chance that something could happen

high-risk pregnancy (high risk)

your pregnancy is called high-risk if you or your baby has an increased chance of a health problem

a pregnancy with a higher than normal risk of developing complications. Risk may be related to a woman's age, a woman carrying multiple fetuses, Rh incompatibility, preterm labour, placenta previa, gestational diabetes, among other conditions.

hind milk

breast milk produced at the end of a feeding. High in calories and fat.

HIV (human immunodeficiency virus)

a disease that destroys certain white blood cells, which can greatly weaken your immune system

When your immune system is weak, you can get serious infections that you normally wouldn't, such as AIDS.



red, itchy, swellings on your skin

Hodgkin's disease (Hodgkin's lymphoma)

cancer in your lymph nodes

Hodgkin's lymphoma — formerly known as Hodgkin's disease — is a cancer of the lymphatic system, which is part of your immune system

home nocturnal hemodialysis

a way to do hemodialysis at home while you sleep


like, alike, similar


a team of people who give care to a person and their family when the person is nearing the end of their life


time when you are in the hospital, time spent in hospital


person or animal

an animal or plant that harbors and provides sustenance for another organism (the parasite)

the recipient of an organ or other tissue derived from another organism (the donor)

HPV (human papillomavirus)

a virus that may cause cervical cancer


to moisten the air

Huntington's disease

a genetic disease that causes nerve cells in your brain to break down.

This causes memory and thinking problems and may change the you act, talk or walk.


high, higher


too much glucose (sugar) in the blood

hyperglycemia while pregnant is usually a sign of gestational diabetes


high cholesterol


a condition where your parathyroid glands work too hard and raises the calcium level in your blood


when an organ or tissue in your body gets bigger


strong reaction


when your body makes more heat than it can handle

Hyperthermia is different from a fever. With a fever, your body raises its temperature on purpose to fight an infection. With hyperthermia, your body temperature rises even though your body doesn't want it to


when your thyroid gland is too active and makes more thyroid hormones than you need


low, lower


low blood sugar


weak reaction


low blood pressure


surgery to remove your uterus (womb)