CBC & TSH Testing

CBCBookmark & Share Printer-friendly version

A complete blood count (CBC) test measures the following:

• The number of red blood cells (RBC count)
• The number of white blood cells (WBC count)
• The total amount of hemoglobin in the blood
• The fraction of the blood composed of red blood cells (hematocrit)

The CBC test also provides information about the following measurements:

• Average red blood cell size (MCV)
• Hemoglobin amount per red blood cell (MCH)
• The amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per red blood cell (MCHC)

The platelet count is also usually included in the CBC. 

How the Test is Performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to Prepare for the Test

There is no special preparation needed.

How the Test Will Feel

When the needle is inserted to draw blood, you may feel moderate pain, though most people feel only a prick or a stinging sensation. Afterward there may be some throbbing or bruising.

Why the Test is Performed

A complete blood count (CBC) is used to detect or monitor many different health conditions. It may be used to:

• Diagnose infections or allergies
• Detect blood clotting problems or blood disorders, including anemia
• Evaluate red blood cell production or destruction

Normal Results

Blood counts may vary with altitude. In general, normal results are:
RBC count:

• Male: 4.7 to 6.1 million cells/mcL
• Female: 4.2 to 5.4 million cells/mcL

WBC count:

• 4,500 to 10,000 cells/mcL

Hematocrit:

• Male: 40.7 to 50.3%
• Female: 36.1 to 44.3%

Hemoglobin:

• Male: 13.8 to 17.2 gm/dL
• Female: 12.1 to 15.1 gm/dL

Red blood cell indices:

• MCV: 80 to 95 femtoliter
• MCH: 27 to 31 pg/cell
• MCHC: 32 to 36 gm/dL

Note:

• cells/mcL = cells per microliter
• gm/dL = grams per deciliter;
• pg/cell = picograms per cell

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

A high RBC or hematocrit may be due to:

• Dehydration (such as from severe diarrhea)
• Kidney disease with high erythropoietin production
• Low oxygen level in the blood for a long time due to heart or lung disease
• Polycythemia vera
• Smoking

A low RBC or hematacrit is a sign of anemia, which can result from:

• Autoimmune diseases such as lupus erythematosus or rheumatoid arthritis
• Blood loss (hemorrhage)
• Bone marrow failure (for example, from radiation, infection, or tumor)
• Chronic kidney disease
• Hemolysis (red blood cell destruction)
• Leukemia and other blood cancers
• Long-term infections such as hepatitis
• Poor diet and nutrition, causing too little iron, folate, vitamin B12, or vitamin B6
• Multiple myeloma

A lower than normal white blood cell count is called leukopenia. A decreased WBC count may be due to:

• Autoimmune diseases (such as systemic lupus erythematosus)
• Bone marrow failure (for example, due to infection, tumor, radiation, or fibrosis)
• Disease of the liver or spleen

High numbers of WBCs is called leukocytosis. It can result from:

• Infectious diseases
• Inflammatory disease (such as rheumatoid arthritis or allergy)
• Leukemia
• Severe emotional or physical stress
• Tissue damage (such as burns)

Low hemoglobin values may be due to:

• Anemia (various types)
• Blood loss

Risks

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Considerations

RBCs transport hemoglobin which, in turn, carries oxygen. The amount of oxygen received by body tissues depends on the amount and function of RBCs and hemoglobin.
WBCs are mediators of inflammation and the immune response. There are various types of WBCs that normally appear in the blood:

• Neutrophils (polymorphonuclear leukocytes)
• Band cells (slightly immature neutrophils)
• T-type lymphocytes (T cells)
• B-type lymphocytes (B cells)
• Monocytes
• Eosinophils
• Basophils

TSH test

Email this page to a friendBookmark & Share Printer-friendly version

A TSH test is a lab test that measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.

How the Test is Performed

A blood sample is needed. For information on how this is done, see: Venipuncture
Other tests that may be done at the same time include:

• T3 test
• Bookmark & Share Printer-friendly version
  Triiodothyronine (T3) is a thyroid hormone. It plays an important role in the body's control of metabolism.
  A laboratory test can be done to measure the amount of T3 in your blood
  

  Normal Results

  The range for normal values is 100 - 200 ng/dL (nanograms per deciliter).
  The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different specimens.Talk to your doctor about the meaning of your specific test results.
  

  What Abnormal Results Mean

  High levels of T3 in the blood may occur in pregnancy, with the use of birth control pills or estrogen, from liver disease, or as part of an inerited condition.
  Higher-than-normal levels of T3 may be a sign of:
  

  • Overactive thyroid gland (for example, Graves disease)
  • T3 thyrotoxicosis (rare)
  • Toxic nodular goiter 

  Lower-than-normal levels may be due to:
  

  • Short- or long-term illness
  • Thyroiditis (swelling or inflammation of the thyroid gland -- Hashimoto's disease is the most common type)
  • Starvation
  • Underactive thyroid gland
   
• T4 test
• T4 (thyroxine) is a hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of T4 in your blood.

• Normal Results

  A typical normal range is 4.5 to 11.2 micrograms per deciliter (mcg/dL).
  Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
  The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
  

  What Abnormal Results Mean

  Greater than normal levels of T4 may be due to conditions that involve an overactive thyroid, including:
• Graves disease
• Germ cell tumors
• High levels of the protein that carries T4 in the blood (can occur with pregnancy, use of birth control pills or estrogen, liver disease, and as part of an inherited condition)
• Iodine-induced hyperthyroidism
• Subacute thyroiditis
• Toxic multinodular goiter
• Trophoblastic disease
• Over-treatment with thyroid hormone medicine

Lower than normal levels of T4 may be due to:

• Hypothyroidism (including Hashimoto's disease and several other disorders involving an underactive thyroid)
• Illness
• Malnutrition or fasting
• Use of certain medications

•  

How to Prepare for the Test

There is no preparation needed for this test. Ask your health care provider about any medicines you are taking that may affect the test results. Do not stop taking any medicines without first asking your health care provider.
Medicines you may need to stop taking include:

• Amiodarone
• Dopamine
• Lithium
• Potassium iodide
• Prednisone

How the Test Will Feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the Test is Performed

Your doctor will order this test if you have symptoms or signs of an overactive or underactive thyroid gland. It is also used to monitor treatment of these conditions.

Normal Results

Normal values can range from 0.4 - 4.0 mIU/L (milli-international units per liter), depending on:

• Your symptoms
• Results of other thyroid lab tests
• Whether you are already being treated for thyroid problems

Even without signs or symptoms of an underactive thyroid (hypothyroidism), you will need to be followed closely by your doctor if your TSH level is over 3.5 mIU/L but your T4 test is normal (called subclinical hypothyroidism).
If you are being treated for a thyroid disorder, your TSH level should be between 0.5 and 2.0 mIU/L.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Higher-than-normal TSH levels are most often due to an underactive thyroid gland (hypothyroidism). There are many causes of this problem.
Lower-than-normal levels may be due to an overactive thyroid gland, which can be caused by:

• Graves disease
• Toxic nodular goiter
• Use of certain medications (including glucocorticoids/steroids, and opioid painkillers such as morphine)

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Alternative Names

Thyrotropin; Thyroid stimulating hormone