Routine lab blood tests are important in the evaluation of
heart failure. These tests can help identify causes of
heart failure; whether other organs, such as the
kidneys and liver, have been affected by the heart failure; or whether
medicines, such as diuretics, have affected the normal electrolyte levels, such
as sodium or potassium levels. The following lab tests may be done in
people with signs or symptoms of heart failure.
A reduced red
blood cell count (anemia) may mean that heart failure is
caused or aggravated by a decrease in the oxygen-carrying capacity of the
blood. A very low blood count may be a sign that anemia is a contributing
factor that is making your heart failure worse. Even if this is not the case, a
low blood count can make your heart work harder and can be dangerous if you
have severe heart failure. Knowing the white blood cell count can be helpful,
because an elevated white count often indicates that you have an infection,
which places additional stress on your heart.
This test measures the
level of a substance in the blood called creatinine. The creatine level can
help determine how well the kidneys are working. Creatinine is excreted in the
urine. High levels of creatinine may indicate that a kidney problem is
responsible for fluid buildup in the body, not heart failure.
A blood urea
nitrogen (BUN) test measures the amount of nitrogen in the blood that comes
from urea. A BUN test helps estimate how well the kidneys are functioning.
Severe heart failure can decrease kidney function. Several common heart failure
medicines?particularly diuretics and angiotensin-converting enzyme (ACE)
inhibitors?can also decrease kidney function.
natriuretic peptide (BNP) test measures the amount of the BNP
hormone in your blood. BNP is made by your heart and
tells how well your heart is working. Normally, only a low amount of BNP is
found in your blood. However, if your heart has to work harder over a long
period of time, such as from
heart failure, the heart releases more BNP and the
blood level of BNP will get higher. The BNP level may drop when treatment for
heart failure is working.
Albumin is a protein in
the body. Decreased levels of this protein may indicate that fluid buildup in
the body is caused by an intestinal disorder (hypoalbuminemia), a liver
problem, or kidney disease.
hormone measurements may be needed if you have a rapid, irregular heartbeat
(atrial fibrillation), have evidence of thyroid disease, or are older than 65.
Abnormal findings may be a sign that heart failure is caused or made worse by
an underactive thyroid (hypothyroidism) or an overactive thyroid
blood glucose test measures the amount of glucose in
your blood after you have not eaten for at least 8 hours. Glucose is a natural
sugar in the body that is used for energy. High levels of glucose in the blood
may indicate diabetes.
A lipid panel is a blood
test that measures
lipids?fats and fatty substances used as a source of
energy in your body. Lipids include
high-density lipoprotein (HDL), and
low-density lipoprotein (LDL).
Liver Function Tests
tests include a variety of tests that measure certain enzymes and other
substances produced by the liver. If the levels of these substances are high,
it may mean damage or disease in the liver. Heart failure may also cause
fluid buildup in the liver, which also may cause elevated liver function test
results. For more information, see the topics
Alanine Aminotransferase (ALT) and
Aspartate Aminotransferase (AST).
People with heart failure need to
maintain the concentration of electrolytes in the blood (particularly sodium,
potassium, and magnesium). This is especially true for people who take
diuretics, which can lower sodium, magnesium, or potassium levels in the blood
if the dose is too high. Other medicines such as ACE inhibitors, by contrast,
can cause high potassium levels.
Your electrolytes should be
checked regularly, particularly if your symptoms are changing or if your
medicines are being adjusted.
A PT or PTT test are blood tests that measure how long it takes blood to clot. These tests can be used to check for bleeding problems. PT is also used to check how medicine to prevent blood clots is working.
A PT test may also be called an INR test.
If you are a sexually active woman of
childbearing age and have new symptoms of heart failure, your doctor may order
a pregnancy test. Pregnancy can sometimes cause heart failure, and pregnancy
and childbirth may be dangerous for a woman who has severe heart failure,
particularly if the heart failure is caused by mitral valve stenosis or other
obstructive heart disease.
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology
Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
How this information was developed to help you make better health decisions.