When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
The hemoglobin test is a common test and is almost always done as part of a complete blood count (CBC). Reasons or conditions for ordering the hemoglobin test include:
Symptoms such as fatigue, poor health, or unexplained weight loss
Signs of bleeding
Before and after major surgery
Chronic kidney disease or many other chronic medical problems
Monitoring of anemia and its cause
Monitoring during treatment for cancer
Monitoring medicines that may cause anemia or low blood counts
Normal results for adults vary, but in general are:
Male: 13.8 to 17.2 grams per deciliter (g/dL) or 138 to 172 grams per liter (g/L)
Female: 12.1 to 15.1 g/dL or 121 to 151 g/L
Normal results for children vary, but in general are:
Newborn: 14 to 24 g/dL or 140 to 240 g/L
Infant: 9.5 to 13 g/dL or 95 to 130 g/L
The ranges 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 health care provider about the meaning of your specific test results.
A rare bone marrow disease that leads to an abnormal increase in the number of blood cells (polycythemia vera)
The body having too little water and fluids (dehydration)
There is little risk involved with having your blood taken.Veins and arteries vary in size from one person 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:
Fainting or feeling lightheaded
Multiple punctures to locate veins
Hematoma (blood buildup under the skin)
Infection (a slight risk any time the skin is broken)
Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.