BLooD 149What Can your blood say about you?
Laboratory blood tests can reveal a great deal about the
functioning of your kidneys and liver, including levels of
electrolytes and other important metabolites. your physician
can build a “risk profile” for heart disease by measuring
blood levels of hDL and LDL cholesterol and blood
lipids called triglycerides. a total blood count would help
determine whether you are anemic or battling an infection.
Some tests, like the “stick” test for monitoring blood
glucose, work with only a few drops of blood. other blood
tests, such as the complete blood count (CBC) listed in
table 8.2, may require several vials of blood. It usually
doesn’t matter whether blood is drawn from an artery or
vein, although veins just inside the elbow or on the top of
the hand are common drawing sites because they are close
to the body surface and easily accessible.
the blood’s chemical makeup is literally a “fluid situation.”
even when a person is completely at rest, the composition
of his or her blood constantly changes as cells, tissues, and
organs carry out basic functions such as taking up oxygen
or nutrients and releasing wastes. to get as clear a picture
as possible of the internal situation that’s being checked,
the physician ordering a blood test may
ask you to fast, avoid caffeine or alcohol,
delay taking medications or vitamins, or
temporarily adjust your usual routine in
some other way. even altitude can affect
the results of testing for the presence of
red blood cells and hemoglobin. In people
who live at high altitiude—where the air
contains less oxygen than at sea level—
the kidneys stimulate the production of
more red blood cells, so more cells and
the hemoglobin they contain circulate in
the bloodstream.
When test results are evaluated, other
factors that can affect test values, such
as a person’s age, weight, and gender,
must be taken into account. For example,
the blood of a female typically contains
less creatinine than is present in a male
of the same age and weight. Creatinine
is formed when muscle cells break
down proteins, and females typically
have less muscle mass than males do.
Laboratories interpret test results using
ranges they have established for normal
and abnormal values. Standard ranges
may vary from laboratory to laboratory, so
it’s important to fully discuss test results
with your doctor. the chart above shows
some ranges for a complete blood count
established by the national heart, Lung,
and Blood Institute.CBC Test Normal Range Results*Red blood cell
(varies with altitude)Male: 5 to 6 million cells/mcL4,500 to 10,000 cells/mcLMale: 14 to 17 gm/dLFemale: 12 to 15 gm/dLMale: 41% to 50%Female: 36% to 44%140,000 to 450,000 cells/mcLFemale: 4 to 5 million cells/mcLWhite blood cellPlateletsHemoglobin
(varies with altitude)Hematocrit
(varies with altitude)
© Cengage Learning
*Cells/mcL 5 cells per microliter; gm/dL 5 grams per deciliter. Hematocrit
measures the percentage of whole blood made up by red blood cells.Useful for Monitoring/
Test Measures Diagnosing
ALb Blood level of albumin Liver/kidney disease,
malnutrition
A1C Blood sugar level Diabetes
bMP Basic Metabolic Panel: Tests Diabetes, kidney
include blood sugar, kidney disease, hypertension
enzymes, electrolytes, blood pH
buN Blood urea nitrogen Kidney function, many
related disorders
CbC Complete Blood Count: Number Anemias, infections
of red blood cells/amount of
hemoglobin, type and number of
white blood cells, platelet count
Allergen-specific Circulating antibodies to Allergies
igE test/RAsT allergens
Creatinine Blood level of creatinine, a Kidney function, many
substance released from related disorders
metabolically active muscle
hiV antibody Circulating antibodies to the HIV infection
human immunodeficiency virus
Lipid profile Blood levels of LDL/HDL Cardiovascular
cholesterol, triglycerides disease risk
P T, AMT PT: Blood-clotting factors made in Hepatitis
the liver; AMT: liver enzyme
Quantitative Circulating human chorionic Pregnancy
hCG hormone (hCG)
Tsh Blood level of thyroid-stimulating Thyroid disorders
hormone (TSH)Table 8.2 some Common blood TestsPhoto: David Scharf/Peter Arnold, Inc.8.6
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