Webster's New World Medical Dictionary

blood poisoning
A bacterial infection of the
blood. See also 
bacteremia; sepsis; septicemia.
blood pressure
The pressure of the blood
within the arteries. Blood pressure is produced pri-
marily by the contraction of the heart muscle. The
traditional measurement of blood pressure is
recorded by two numbers. The first number (the
systolic pressure) is measured after the heart con-
tracts, and it is the higher number. The second num-
ber (the diastolic pressure) is measured before 
the heart contracts, and it is the lower number. A
blood pressure cuff is used to measure pressure.
See also 
hypertension; hypotension; sphygmo-
manometer.
blood pressure, high
See 
hypertension.
blood pressure, low
See 
hypotension.
blood sugar, high
See 
hyperglycemia.
blood sugar, low
See 
hypoglycemia.
blood test
A test that requires a sample of blood.
Some blood tests require only a finger stick, and
others require a venipuncture (blood taken from a
vein) or blood withdrawn from an artery.
blood thinner
An anticoagulant agent; a medica-
tion that works against coagulating process of
blood.
blood titer
A blood test that tests for the level, or
amount (titer), of something in the blood. For
example, a strep titer looks for the level of strepto-
coccus antibodies in the blood.
blood transfusion
The transfer of blood or
blood components from one person (the donor)
into the bloodstream of another person (the recipi-
ent). Blood transfusion may be done as a lifesaving
maneuver to replace blood cells or blood products
lost through bleeding or due to depression of the
bone marrow. Transfusion of one’s own blood
(autologous) is the safest method but requires
advanced planning, and not all patients are eligible
for it. Directed donor blood allows the patient to
receive blood from known donors. Volunteer donor
blood is usually most readily available and, when
properly tested, has a low risk of side effects.