An Hgb blood test measures a person’s hemoglobin levels. This protein helps red blood cells carry oxygen and keep cells and organs functioning. Low hemoglobin is known as anemia.

Hemoglobin is also what gives red blood cells their color.

If an Hgb blood test reveals that an individual’s hemoglobin is not within the normal range, a doctor may use further tests to check for possible blood disorders.

According to the National Heart, Lung, and Blood Institute, anemia — another term for low hemoglobin — is the most common blood disorder in the United States, affecting more than 3 million people.

An Hgb blood test involves analyzing an individual’s blood to see how much hemoglobin it contains.

The first step in the process is drawing blood. A healthcare provider, typically a nurse, will use a needle to collect the person’s blood.

They will then label the blood sample and send it off for analysis.

If the Hgb blood test reveals abnormal levels of hemoglobin, doctors may order further tests. These may include a complete blood count to provide more information about the number and type of all the cells in the blood.

A doctor may also order a hematocrit test, as this test focuses solely on red blood cells, which is where hemoglobin occurs. The hematocrit test measures what proportion of the blood the red blood cells represent.

An Hgb test can be a part of a routine checkup, or a doctor may order it if an individual is showing signs and symptoms that could be due to abnormal levels of hemoglobin.

They may order an Hgb test if a person is experiencing symptoms of anemia, for example. Anemia occurs when hemoglobin levels are low.

A doctor may also ask for an Hgb test to ensure that the treatment for abnormal hemoglobin levels is effective.

If a person’s hemoglobin levels are higher or lower than the figures below, they may have a medical condition.

The medical community typically defines the normal ranges of hemoglobin as follows:

  • Children: 11–16 grams per deciliter (g/dl)
  • Females: 12–15 g/dl
  • Males: 13.5–18 g/dl
  • Pregnant women: Usually higher than 10 g/dl

The typical percentage of red blood cells in the blood ranges from 37% – 49%.

Some factors can affect the results of an Hgb test. These include:

  • medications
  • a person’s menstrual cycle
  • lifestyle choices, such as diet and exercise
  • a recent blood transfusion

Learn more about hemoglobin levels here.

When a person has high levels of hemoglobin, doctors refer to this as polycythemia.


The symptoms of polycythemia include:

  • headaches
  • tiredness
  • shortness of breath
  • enlarged spleen

A person may also experience pruritis, or itching, on the back after a warm shower.


Factors that can cause high levels of hemoglobin include:

  • living at a high altitude
  • smoking
  • dehydration
  • lung disease
  • liver disease
  • congenital disabilities in the heart that interfere with oxygenated blood
  • chronic obstructive pulmonary disease (COPD)
  • extremely intense exercise
  • polycythemia vera, a rare disease that causes the body to produce too many red blood cells

Anemia is another term for low hemoglobin.


The symptoms of anemia include:


Possible causes of a low hemoglobin reading in an Hgb blood test include:

  • significant loss of blood as a result of trauma, surgery, or ongoing internal bleeding
  • ulcers
  • heavy periods
  • bone marrow problems, due to cancers such as leukemia
  • cancers such as colon cancer, which can cause internal bleeding, and lymphoma, which damages the bone marrow
  • kidney failure, which interferes with the production of hemoglobin
  • Crohn’s disease and ulcerative colitis
  • thalassemia, which occurs when the body is unable to produce enough hemoglobin
  • sickle cell anemia
  • chronic inflammation
  • a diet deficient in iron, vitamin B-12, and folate

An Hgb blood test can provide important information about an individual’s health.

The person’s outlook depends on whether their hemoglobin is high, low, or normal and on what is causing any irregularities that the test has revealed.

Routine blood tests can sometimes reveal serious health problems before symptoms develop and make early, lifesaving intervention possible.

Below are frequently asked questions regarding HGB tests.

What does Hgb mean in a blood test when it is low?

Low Hgb levels mean a person has anemia – a lack of healthy blood cells in their body. This can lead to fatigue, paleness, shortness of breath, and fainting.

What does it mean if your Hgb is high?

High Hgb levels mean a person has polycythemia. This can cause headaches, tiredness, and dizziness.

What level of Hgb is concerning?

Typical Hgb levels for adults are 12–18 g/dl, although these vary depending on a person’s sex and health status. Hgb levels outside of this range require medical assessment.

What should I do if my hemoglobin is low?

Eating more foods rich in iron and folate or supplementing if necessary can often raise a person’s Hgb levels. However, if an underlying condition is causing abnormal Hgb levels, treating this will be the main course of action.

An Hgb blood test is a routine medical procedure that doctors sometimes include as part of a regular physical examination.

The test measures how much hemoglobin is in an individual’s blood, and it is a very important health indicator.

Many different factors can lead to abnormal Hgb readings, and the treatment will depend on the cause.