Health Encyclopedia


Health Encyclopedia Home

Why the Doctor Takes a Blood Sample

Why the Doctor Takes a Blood Sample

You probably don't enjoy giving a blood sample, but it's an important part of a physical exam. From a small sample of your blood, your health care provider can order scores of tests and find out a lot about your overall health.

Here are four common tests, according to the American Association of Clinical Chemistry: blood lipid level, complete blood cell count (CBC), blood sugar level, and thyroid function tests.

Blood lipid level. The levels of total cholesterol, LDL (low density lipoprotein cholesterol), and HDL (high density lipoprotein cholesterol) in your blood may indicate your chances of someday developing heart disease. Cholesterol, a soft, fat-like substance found in the cell walls of all animals, can stick to the walls of arteries and form plaques. These plaques can hamper and even block the flow of blood to the heart. A high total cholesterol and/or a high LDL level means you probably need to exercise more and cut back on foods high in saturated fat and cholesterol. Your doctor may also recommend medication.

Complete blood cell count. The red cells in your blood carry the oxygen that body tissues need to function. The CDC includes tests of the red cells called Hemoglobin and Hematocrit. If these are low, anemia is present. Anemia can account for fatigue, paleness, shortness of breath, and even drowsiness. Women are more susceptible to anemia. Childbirth can bring on anemia because bleeding during the birth process may deplete the body's supply of iron, which is essential for red blood cells. Menstruation can also reduce a woman's red blood cell count. Anemia can be treated. The CBC will also test for white cells, which are responsible for fighting infection.

Blood sugar. A high blood sugar level may indicate that you need further testing to look for diabetes, a disease with sometimes subtle symptoms. Diabetes, if untreated, can lead to blindness and other medical complications. Symptoms of diabetes include excessive thirst, more frequent urination, and fatigue. If detected early, diabetes can be treated to lessen its impact on health.

Thyroid. This gland at the base of your neck produces a hormone that controls your metabolism. With too little of the hormone, you feel tired and gain weight easily. With too much of the hormone, you feel jittery, your heart may beat rapidly, and you lose weight.

For these four tests, your health care provider only needs about two small vials of blood. In most cases, a nurse or a medical specialist called a phlebotomist draws the blood sample with a needle inserted in a vein in your arm. The procedure takes only a few minutes.

Related Items
Content Type 167
  Acetylcholine Receptor Antibody (Blood)
  Albumin (Blood)
  Alpha-Fetoprotein (Blood)
  Alpha-Fetoprotein Tumor Marker (Blood)
  Amphetamine Screen (Blood)
  Amylase (Blood)
  Angiotensin Converting Enzyme (Blood)
  Antidiuretic Hormone
  Antimitochondrial Antibody and Antimitochondrial M2 Antibody
  Apolipoprotein A
  Apolipoprotein B100
  Benzodiazepines (Blood)
  Direct Bilirubin
  BNP (Blood)
  C-Peptide (Blood)
  CA 125
  CA 19-9
  CA 27-29
  Calcium (Blood)
  Carcinoembryonic Antigen
  Cardiac Biomarkers (Blood)
  Total and Free Carnitine
  Catecholamines (Blood)
  Ceruloplasmin (Blood)
  Cholinesterase (Blood)
  Clonazepam Drug Level (Blood)
  Creatine Kinase (Blood)
  Creatinine Clearance
  Creatinine (Blood)
  Cystatin C
  Dehydroepiandrosterone and Dehydroepiandrosterone Sulfate
  Digoxin Drug Level
  Erythropoietin (Blood)
  Estradiol (Blood)
  Ethanol (Blood)
  Ferritin (Blood)
  Fluphenazine Drug Level (Blood)
  Follicle-Stimulating Hormone
  Free Androgen Index
  Growth Hormone with Stimulation (Blood)
  Growth Hormone with Suppression (Blood)
  Growth Hormone (Blood)
  HCG (Blood)
  HDL Cholesterol
  Insulin-Like Growth Factor
  Total and Free Insulin (Blood)
  Iron (Blood)
  Iron and Total Iron-Binding Capacity
  Ketone Bodies (Blood)
  Lactose Tolerance (Blood)
  LDL Cholesterol
  Adult Lead (Blood)
  Lead (Blood)
  Leptin (Blood)
  Lipid Panel with Non-HDL Cholesterol
  Lipoprotein-Associated Phospholipase A2
  Lipoprotein(a) Cholesterol
  Luteinizing Hormone (Blood)
  Magnesium (Blood)
  Mercury (Blood)
  Metanephrines (Blood)
  Methylmalonic Acid (Blood)
  Myoglobin (Blood)
  Pancreatic Polypeptide
  Parathyroid Hormone
  Proinsulin (Blood)
  Prolactin (Blood)
  Salicylate (Blood)
  Free Light Chains (Blood)
  Sodium (Blood)
  Free and Bound Triiodothyronine (Blood)
  Free and Bound T4
  Tartrate-Resistant Acid Phosphatase
  Tegretol (Blood)
  Free Testosterone
  Total Testosterone
  Thyroid Antibody
  Thyroid Antithyroglobulin Antibody
  Thyroid Stimulating Hormone
  Total Copper (Blood)
  Tricyclic Antidepressant Screen
  Trypsin (Blood)
  Blood Urea Nitrogen
  Uric Acid (Blood)
  VLDL Cholesterol