Last updated on 12th Sep 2022 - By Dwayne Michaels

Why is my rbc high or low?

The rbc results are interpreted along with the results for hemoglobin, hematocrit(PCV), MCV and RDW to help diagnose disease severity. So let's know about all these tests and let's try to know the real cause of your disease.

After reading this article thoroughly you will be able to self-diagnose your disease

Before understanding Hemoglobin, Hematocrit (PCV) and RBC, let us know about some of the causes of abnormal blood cells.

Low hemoglobin + Low RBC count + Low hematocrit can be caused by:

  • Bone marrow damage
  • Destruction of red blood cells
  • Thalassemia
  • Chronic inflammatory diseases
  • Chronic bleeding from sites such as the digestive tract (e.g., ulcers, polyps, colon cancer)
  • Iron, folate or B12 deficiency
  • Bone marrow disorders such as aplastic anemia, myelodysplastic syndrome, or cancers such as leukemia, lymphoma, multiple myeloma
  • Kidney failure

High hemoglobin + High RBC count + High hematocrit can be caused by:

  • Congenital heart disease
  • Lung disease
  • Kidney tumors that produce excess erythropoietin
  • Smoking
  • Polycythemia vera
  • Genetic causes
  • Living at high altitudes

If you need our help diagnosing the severity of your illness and want to fix your problem, you can upload your blood report here. Upload blood test report now

Let's know about these blood tests:


A healthy individual human has 12 to 20 grams of hemoglobin in every 100 mL of blood.

The hemoglobin test measures the amount of hemoglobin your sample of blood. A hemoglobin level can be performed alone or with a hematocrit, a test that measures the proportion of blood that is made up of RBCs, to evaluate your red blood cells.

Hemoglobin deficiency can be caused either by a decreased amount of hemoglobin molecules, as in anemia, or by decreased ability of each molecule to bind oxygen at the same partial pressure of oxygen.

Other common causes of low hemoglobin include loss of blood, nutritional deficiency, bone marrow problems, kidney failure, or abnormal hemoglobin (such as that of sickle-cell disease).

Decrease of hemoglobin, with or without an absolute decrease of red blood cells, leads to symptoms of anemia.

Elevated levels of hemoglobin are associated with increased numbers or sizes of red blood cells, called polycythemia. This elevation may be caused by congenital heart disease, cor pulmonale, pulmonary fibrosis, too much erythropoietin, or polycythemia vera. High hemoglobin levels may also be caused by exposure to high altitudes, smoking, dehydration, advanced lung disease and certain tumors.

Hemoglobin is the iron-containing protein found in all red blood cells (RBCs) that gives the cells their characteristic red color. Hemoglobin enables RBCs to bind to oxygen in the lungs and carry it to tissues and organs throughout the body. It also helps transport a small portion of carbon dioxide, a product of cell metabolism, from tissues and organs to the lungs, where it is exhaled.

If you need our help diagnosing the severity of your illness and want to fix your hemoglobin problem, you can upload your blood report here. Upload blood test report now


Red blood cells (RBCs), also called erythrocytes, are cells that circulate in the blood and carry oxygen throughout the body.

Red blood cells, which make up about 40% (ranging 37-49%) of the blood's volume, are produced in the bone marrow and are released into the bloodstream when they are, or nearly are, mature. The typical lifespan of an RBC is 120 days, and the bone marrow must continually produce new RBCs to replace those that age and degrade or are lost through bleeding.

Changes in the RBC count usually mirror changes in other RBC tests, including the hematocrit and hemoglobin level.

If RBCs are lost or destroyed faster than they can be replaced, if bone marrow production is disrupted, or if the RBCs produced do not function normally, or do not contain enough hemoglobin, then you may develop anemia, which affects the amount of oxygen reaching tissues.

If too many RBCs are produced and released, then you can develop polycythemia. This can cause thicker blood, decreased blood flow and related problems, such as headache, dizziness, problems with vision, and even excessive clotting or heart attack.

A CBC may also be performed on a regular basis to monitor people who have been diagnosed with conditions such as:

  • Bone marrow disorders
  • Kidney disease
  • Bleeding problems
  • Chronic anemia
  • Polycythemia
  • Cancer, as chemotherapy or radiation therapy often decreases bone marrow production of all the blood cells

A rise or drop in the RBC count must be interpreted in conjunction with other tests, such as hemoglobin, hematocrit, reticulocyte count, and/or red blood cell indices.

Causes of a low RBC count:

  • Loss of blood
  • Hemolytic anemia caused by autoimmunity or defects in the red cell itself
  • Kidney failure
  • Chronic inflammatory disease
  • Sudden or chronic bleeding from the digestive tract (e.g., ulcers, polyps, colon cancer) or other sites
  • Bone marrow damage
  • Iron deficiency, vitamin B12 or folate deficiency
  • Bone marrow disorders such as leukemia, multiple myeloma, myelodysplastic syndrome, or lymphoma or other cancers that spread to the bone marrow

Causes of a high RBC count:

  • Dehydration
  • Lung disease
  • Congenital heart disease
  • Smoking
  • Kidney tumor that produces excess erythropoietin
  • Polycythemia vera

An RBC count can be used to detect a problem with red blood cell production and/or lifespan, but it cannot determine the underlying cause. In addition to the full CBC, some other tests may be performed at the same time or as follow up to help establish a diagnosis. Examples include:

  • Blood smear
  • Reticulocyte count
  • Iron studies
  • Vitamin B12 and folate levels
  • In more severe conditions, a bone marrow aspiration and biopsy

Red blood cells may be given as part of a blood transfusion. Blood may be donated from another person, or stored by the recipient at an earlier date. Donated blood usually requires screening to ensure that donors do not contain risk factors for the presence of blood-borne diseases, or will not suffer themselves by giving blood.

Many diseases involving red blood cells are diagnosed with a blood film (or peripheral blood smear), where a thin layer of blood is smeared on a microscope slide.

If you need our help diagnosing the severity of your illness and want to fix your RBC problem, you can upload your blood report here. Upload blood test report now

Hematocrit (also called PCV or Packed Cell Volume):

A hematocrit is a test that measures the proportion of your blood that is made up of red blood cells (RBCs).

It is normally 40.7–50.3% for males and 36.1–44.3% for females. There are other names for the hematocrit, such as packed cell volume (PCV), volume of packed red cells (VPRC), or erythrocyte volume fraction (EVF).

Blood consists of RBCs, white blood cells (WBCs), and platelets suspended in a fluid portion called plasma. The hematocrit is a ratio of the volume of red blood cells to the volume of all these components together, called whole blood. The value is expressed as a percentage or fraction. For example, a hematocrit value of 40% means that there are 40 milliliters of red blood cells in 100 milliliters of whole blood.

Hematocrit levels also serve as an indicator of health conditions. Thus, tests on hematocrit levels are often carried out in the process of diagnosis of such conditions, and may be conducted prior to surgery. Additionally, the health conditions associated with certain hematocrit levels are the same as ones associated with certain hemoglobin levels.

If the number and/or size of RBCs decreases, so will the hematocrit and vice versa. In general, the hematocrit will rise when the number of red blood cells increases and the hematocrit will fall to less than normal when there is a decrease in RBCs.

Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions.

The hematocrit can indicate if there is a problem with RBCs, but it cannot determine the underlying cause. In addition to CBC, some other tests may also be needed to diagnose the problem. Some tests include : Reticulocyte count, iron studies, vitamin B12 and folate levels, and in more serious situations, bone marrow exams.

If you need our help diagnosing the severity of your illness and want to fix your hematocrit problem, you can upload your blood report here. Upload blood test report now