What is a hemoglobin (HGB) blood test?

What is HGB? | Normal HGB levels | Factors that affect HGB | Low HGB | High HGB

Hemoglobin, often abbreviated as Hb or Hgb, is an essential protein in red blood cells of your blood. It plays a vital role in transporting oxygen to your tissues, and to make sure your tissues always have the oxygen they need to function, you must maintain a consistent and healthy hemoglobin level. Your healthcare provider will order a hemoglobin blood test to check for this periodically, typically at least at your routine annual checkup, and perhaps more frequently.

The hemoglobin blood test is a part of a complete blood count lab test, commonly referred to as the CBC, which looks at different components of your blood, including your red blood cells, white blood cells, and platelets. These laboratory tests are very common.

What is HGB?

Hemoglobin is a protein in the red blood cells responsible for carrying oxygen in the blood to the tissues of a person. We test your hemoglobin levels because it is essential to ensure you have enough hemoglobin to consistently maintain good oxygenation in your body. If your hemoglobin levels are too low, you are considered anemic. There are ways to correct anemia to ensure your tissues remain healthy, but it’s best to be aware as soon as possible so you may take corrective action. Knowing the symptoms of anemia may help you identify the issue sooner.

Hematocrit level is a related measurement in the CBC your healthcare provider will consider. While hemoglobin tests measure the amount of hemoglobin in whole blood, hematocrit measures the volume of red blood cells compared to the total blood volume expressed as a percentage. Both tests can be affected by a patient’s fluid status. A dehydrated patient will have hemoglobin and hematocrit levels that appear higher than those with normal volume status. In comparison, a patient who is fluid-overloaded will have hemoglobin and hematocrit levels that appear lower than a normal volume status patient.

Normal HGB levels

Hemoglobin levels are reported in your lab values in grams per deciliter (gm/dL). Your gender at birth is a factor in determining your normal value range. Normal hemoglobin levels for adult men are higher than normal levels for adult women. Populations at higher altitudes tend to have higher baseline hemoglobin and hematocrit values upon blood testing. Thus geographic location is accounted for by your healthcare provider when interpreting the results. Remember, these are common measurements in blood work done as a part of a routine checkup. 

Factors that affect HGB

There are other factors which can affect your hemoglobin levels. These can include your age, medications, and any inflammation in your body. Your healthcare provider will likely try to get as much medical history from you as they can to assess your lab values.

Low HGB levels

Low hemoglobin levels are those hemoglobin test results that fall below the normal range for the patient’s sex and age group. When this occurs, the patient is considered anemic. 

Causes of Low Hb

• Blood loss (from trauma or other high volume systemic bleeding)
• Malnutrition
  • Low iron
  • Low B-12
  • Low folate
• Chronic inflammation
• Genetic causes
• Infectious diseases
• Concurrent drug therapies
• Bone marrow suppression
• Autoimmune disease

Symptoms of Low Hb

The symptoms of low hemoglobin can vary in presentation and severity depending on the patient. Unfortunately, they are sometimes very non-specific and may be mistaken as being associated with another cause. Anemic patients typically experience fatigue, dizziness, and weakness. They may complain of headaches or appear with a yellowish color to the skin or white of the eyes which we refer to as jaundice. Other more bothersome symptoms are heart palpitations or a racing heartbeat, chest pain, or shortness of breath. Anemic patients tend to have cold extremities, meaning if you were to touch their hands or feet, they are cooler to the touch than the rest of their body or in comparison to yours. 

A low hemoglobin level means you are at risk for poor oxygenation of your tissues. Your tissues need oxygen to survive, so a consistently low or dangerously low hemoglobin level concerns your healthcare provider. Anemia can lead to heart problems such as irregular heartbeat, enlarged heart, or even heart failure. It can also leave you vulnerable to infections or lead to complications in pregnancy. Anemia is a medical condition that can be serious if not corrected, so it is important to intervene and correct it as soon as possible.

Treatment of Low Hb

Treating your low hemoglobin levels will require a better understanding of the cause. If your low hemoglobin is caused by a particular medication you take, your medical team may look at alternative medications that don’t affect your hemoglobin levels. If you have an autoimmune disease related to your low hemoglobin levels, your hemoglobin levels can be corrected by treating your autoimmune disease with appropriate therapy.

There are some rare times when more extreme measures must be taken to correct hemoglobin levels and treat anemia, such as a blood transfusion or a blood or bone marrow transplant. If you are bleeding internally or from trauma, it may require surgery to stop the blood loss. 

Patients who are anemic are often asked to make sure their daily diet and supplement routine contains adequate amounts of vitamin B-12 and iron. Too much iron can have negative effects, so make sure your healthcare provider guides your decision on which iron to take and how much.

High HGB levels

Causes of High Hb

• Cancer (liver, kidney, blood)
• Chronic obstructive pulmonary disease (COPD)
• Dehydration
• Heart disease (heart failure)
• Exposure to carbon dioxide

Associations of High Hb

• Smoking
• Obesity
• Living in higher altitudes
• High blood glucose (blood sugar) levels
• High total cholesterol levels

Symptoms of High Hb

The symptoms of a high hemoglobin level may look a lot like a low hemoglobin level in some patients with headaches and dizziness being some of the most common, but also somewhat nondescript. There may also be unexplained weight loss, joint swelling, or excessive sweating. Patients who are only slightly elevated or on the higher side of normal have reported higher physical energy levels and physical performance, but sustained high hemoglobin levels above the normal range can be dangerous. 

Erythrocytosis is having a high concentration of red blood cells. This condition can be due to a physical cause such as dehydration, but it can also be due to more serious causes such as polycythemia vera, a blood cancer. Conditions like erythrocytosis are why your doctor will look at more blood results than just hemoglobin to make a determination about your health and the cause of any issues they are seeing. They may assess you in a physical examination for bruising, changes to your nail beds, or skin changes. All of these things together will help them make a medical determination on the results of your hemoglobin reading.

Treatment of High Hb

If your high hemoglobin is due to your hydration status, one of the most effective and natural things you can do is restore your body’s healthy fluid status. Drink plenty of water and avoid alcohol and other liquids or foods which may further dehydrate you, like those high in sugar. 

Phlebotomy remains a critical part of treatment. It involves the physical removal of red blood cells from your circulation via a needle in your vein. 

Hydroxyurea is second-line treatment when phlebotomy is not an option or isn’t adequate alone. However, neutrophil counts must be monitored while on hydroxyurea.

Your doctor will devise the appropriate treatment plan for you. This is not intended to be medical advice.

The bottom line

Hemoglobin plays a critical role in the body, and it is important to complete your blood work regularly as ordered by your physician to make sure your blood is well equipped to oxygenate all of your vital organs and tissues. Look for signs and discuss with your doctor if you feel your hemoglobin levels may be too high or too low. It is easy to confirm with a blood test, and oftentimes small lifestyle interventions can make the corrections needs to get patients within normal range when it is caught early enough.