Hemoglobin Test
Overview
A hemoglobin test measures how much hemoglobin is in the blood. Hemoglobin is a protein inside red blood cells. It has an important job: carrying oxygen from the lungs to other parts of the body, and bringing carbon dioxide back to the lungs to be removed.
| Key Parts | Description |
|---|---|
| Hemoglobin | Oxygen-carrying protein in red blood cells |
| Red Blood Cells | Cells that have hemoglobin inside them |
| Plasma | Liquid part of blood surrounding the cells |
| Hemoglobin Test | Measures hemoglobin amount in blood |
Low hemoglobin levels may show anemia. Anemia can happen if blood loss occurs, important nutrients are lacking, or ongoing health conditions exist. Common nutrients that affect hemoglobin levels are iron, vitamin B12, and folate.
High hemoglobin can point to erythrocytosis. Reasons for high hemoglobin include living at high altitudes, smoking, sleep apnea, inherited health conditions, dehydration, or some types of bone marrow cancer such as polycythemia vera.
Reasons for Having the Test
Doctors often include a hemoglobin test during a routine checkup as part of a complete blood count. This helps check a person’s general health and can spot early signs of health issues.
Doctors use this test to understand symptoms like tiredness, weakness, dizziness, or shortness of breath. These symptoms could signal anemia or other blood-related problems.
People with blood conditions such as anemia or polycythemia vera may need this test often. Healthcare teams use it to track changes over time and make treatment choices easier.
Key reasons a hemoglobin test is done:
| Purpose | Example Use |
|---|---|
| General health screening | Routine checkup |
| Finding causes of symptoms | Investigating fatigue or dizziness |
| Monitoring known blood disorders | Tracking anemia or polycythemia vera |
Getting Ready for the Test
Most people, including children and adults, do not need to change their regular eating or drinking habits before a hemoglobin test. However, if other tests happen at the same time, fasting might be required. Always follow the instructions the healthcare team provides.
Tips
- Take usual medications unless told otherwise.
- Comfort infants and young children before the test.
- Bring any questions to the staff.
What Happens During the Procedure
When a hemoglobin test occurs, a healthcare worker collects a blood sample. They usually use a needle to draw blood from a vein in the arm or hand. For babies, they use a quick prick on the heel or finger instead.
After the Blood Is Taken
- The sample goes to a lab for analysis with an Hgb meter.
- The patient may rest for a short time.
- Staff check for dizziness or discomfort.
Most people can return to normal activities soon after the test. The whole process is quick and only takes a few minutes.
Results
Hemoglobin Values Below the Normal Range
Hemoglobin levels above the normal range may suggest polycythemia, a condition where the bone marrow produces too many red blood cells. This thickens the blood and raises the risk of clots. Other possible causes include:
- Nutrient Deficiency: Not enough iron, vitamin B12, or folate in the diet can lower hemoglobin levels.
- Blood Loss: Bleeding, including heavy periods or hidden bleeding in the digestive system, often leads to low results.
- Chronic Conditions: Diseases such as kidney or liver problems, low thyroid hormones, or certain cancers like leukemia can cause anemia.
- Inherited Disorders: Issues like thalassemia reduce the amount of hemoglobin but not the number of red cells.
If someone has a history of anemia and their levels drop, they may need to change treatment. Healthcare professionals can help decide the next steps. Sometimes more tests, such as hematocrit measurement or a quantitative determination of hemoglobin, help find the cause.
Possible Related Tests
| Test Name | Purpose |
|---|---|
| Hematocrit | Determines the percentage of red blood cells present in the bloodstream. |
| Hemoglobin A1c (HbA1c) | Checks long-term blood sugar control, especially for diabetes. |
| Iron studies | Looks for iron deficiency. |
| Vitamin B12/folate | Assess for anemia resulting from vitamin deficiencies. |
Hemoglobin Values Above the Normal Range
Higher than normal hemoglobin values can point to problems such as polycythemia. In polycythemia vera, the bone marrow creates too many red blood cells. This makes the blood thicker and can increase the risk of clots. Other possible causes for high hemoglobin:
- Lung Diseases: Chronic illnesses can cause the body to make more red blood cells to carry extra oxygen.
- Dehydration: Less fluid in the blood will raise the hemoglobin concentration.
- High Altitude: The body reacts by making more hemoglobin for the lower oxygen levels.
- Heavy Smoking or Burns
- Certain Drugs: Using erythropoietin or similar medicines.
For patients with polycythemia vera or other known disorders, elevated results may mean the current management plan needs to be reviewed. Doctors may recommend further testing, such as monitoring hematocrit levels.
Some people may naturally have higher values due to living at elevation or intensive athletic training. Common symptoms of high hemoglobin include:
- Headaches
- Dizziness
- Itchiness (especially after a hot shower)
- Joint pain
If hemoglobin levels are outside the healthy range, healthcare teams use a combination of lab tests and medical history to better understand the cause. Asking questions about your results and how they relate to conditions like anemia, polycythemia, or diabetes (if an A1c test is included) can help guide your care.
