Dec 18, 2011
This information is from the Mayo Clinic's website:
A hemoglobin test measures the amount of hemoglobin in your blood. Hemoglobin is a protein in your red blood cells that carries oxygen to your body's organs and tissues and transports carbon dioxide from your organs and tissues back to your lungs.
If a hemoglobin test reveals that your hemoglobin level is lower than normal, it means you have a low red blood cell count (anemia). Anemia can have many different causes, including vitamin deficiencies, bleeding and chronic diseases.
If a hemoglobin test shows a higher than normal level, there are several potential causes, such as the blood disorder polycythemia vera, living in a high altitude, smoking, dehydration, burns and excessive vomiting.
The normal range for hemoglobin is:
• For men, 13.5 to 17.5 grams per deciliter (135 to 175 grams per liter)
• For women, 12.0 to 15.5 grams per deciliter (120 to 155 grams per liter)
Normal ranges for children vary with age and sex. The range for a normal hemoglobin level may differ from one medical practice to another.
Lower than normal results
If your hemoglobin level is lower than normal, you have anemia. There are many forms of anemia, each with different causes. Causes of anemia can include:
• Iron deficiency
• Vitamin B-12 deficiency
• Folate deficiency
• Cancers that affect the bone marrow, such as leukemia
• Kidney disease
• Liver disease
• Thalassemia — a genetic disorder that causes low levels of hemoglobin and red blood cells
If you've been previously diagnosed with anemia, a hemoglobin level that's lower than normal may indicate a need to alter your treatment plan.
Higher than normal results
If your hemoglobin level is higher than normal, it may be the result of:
• Polycythemia vera — a blood disorder in which your bone marrow makes too many red blood cells
• Lung disease
• Living at a high altitude
• Heavy smoking
• Excessive vomiting
• Extreme physical exercise
If you've been previously diagnosed with polycythemia vera, an elevated hemoglobin level may indicate a need to alter your treatment plan.
If your hemoglobin level is below or above normal, your doctor may want to evaluate the hemoglobin test results along with those of other tests, or additional tests may be necessary, to determine next steps.
Hematocrit is the proportion of your total blood volume that is composed of red blood cells. A hematocrit (Hct) test indicates whether you have too few or too many red blood cells — conditions that can occur as the result of certain diseases. Red blood cells, or erythrocytes, transport oxygen throughout your body.
A hematocrit test is done using a sample of your blood. A lab technician puts the sample in a device called a centrifuge that spins the blood very quickly in a test tube. This motion separates your blood into three parts: the fluid component (plasma), red blood cells and other blood cells. When the blood is separated, the technician can determine what proportion of the cells are red blood cells. Hematocrit is also called packed-cell volume (PCV).
Results from your hematocrit are reported as the percentage of blood cells that are red blood cells. The normal range is 38.8 to 50 percent for men and 34.9 to 44.5 percent for women. The normal range for children 15 years of age and younger varies by age and sex. The lower and upper thresholds for a normal hematocrit value may vary somewhat from one medical practice to another.
The result of your hematocrit test is just one piece of information that helps your doctor assess your health. Talk to your doctor about what your hematocrit test result means in light of the symptoms you're experiencing and the results of other diagnostic tests.
A number of conditions can affect the outcome of a hematocrit test and yield inaccurate or misleading results. These complicating factors include:
• Living at a high altitude
• Significant recent blood loss
• Recent blood transfusion
• Severe dehydration
Your doctor will take into account possible complicating factors when interpreting the results of your hematocrit test. Your doctor may want to repeat the hematocrit test and do other blood tests if results provide conflicting or unexpected information.