Normal Hematocrit Levels

Normal Hematocrit Levels and Hemoglobin


Normal Hematocrit levels and Hematocrit Normal Range vary from one person to another based on the person’s age and sex. Males tend to have higher Normal Hematocrit  Levels than females do. The Normal  Hematocrit Level also tend to decrease with aging. High and Low Hematocrit Levels may occur due alternation in the normal red blood Cells count or alternations to the normal Red Blood Cells Size. Normal Hematocrit Levels are very close to the Normal Hemoglobin Levels. Within a Normal size of the Red Blood Cells, knowing the Hematocrit Level would help knowing the Hemoglobin Level and vise versa. This will be explained in details after understanding how Hematocrit Levels are measured.


Measuring Hematocrit Levels

Normal Hematocrit Levels

Hematocrit Level is the percentage ratio between the height of packed RBC in a centrifuged blood tube to the height of the original blood.

When a tube of human blood is exposed to Centrifugal Force, the blood in the Centrifuged tube will be broken down into 3 visibly recognizable components; yellow transparent liquid of blood plasma, a small greyish white thin layer of white blood cells and platelets known as the Buffy Coat, and the heavy Red Blood Cells accumulate at the bottom of the blood tube (See illustration).

Hematocrit Levels are then calculated as the percentage ratio of the height of the Red Blood Cells column in the

centrifuged blood tube to the original height of the blood in the same tube before centrifugation.

Hemoglobin and Hematocrit Levels

Hemoglobin and Hematocrit Levels are very close that a relationship is noticed between Hemoglobin and Hematocrit Levels. To have a better idea about how healthy are the Red Blood Cells of a person, doctors order both of Hemoglobin and Hematocrit tests together (Also known as Hgb and Hct tests).

Hemoglobin is the protein of Red Blood Cells that carries and transfers Oxygen and Nutrition to the various organs and tissues of human body. Hemoglobin Levels measures the concentration of Hemoglobin in the human blood in terms of grams per deciliter (g/dl).

As I have mentioned previously, Hematocrit Levels are a visual indication of the volume of Red Blood Cells compared to the total volume of the blood sample. This volume (Hematocrit Level in other word) depends on:

  • Red Blood Cells Count. As the count of Red Blood cells increase, the volume of the red blood cells inside a centrifuged blood tube increases leading to High Hematocrit Levels. And the opposite is definitely right, low Red Blood Cells count will lead to low hematocrit levels.
  • The size and shape of Red Blood Cells can affect the Hematocrit Levels. Abnormally large Red Blood Cells (the case of Macrocytic Anemia for example) will increase the volume of the packed red blood cells in a centrifuged blood tube leading to High Hematocrit Levels.

Within a normal size of Red blood Cells, the Hematocrit Level percentile should approximately equals 3 times the Hemoglobin Level in terms of grams per deciliter (g/dl). For example a person with a %45 Hematocrit Level is expected to have an approximate Hemoglobin Level of 15 g/dl and a person who has a Hemoglobin level of 12g/dl is expected to have an approximately %36 Hematocrit Level.

Alternations to this relationship between Hemoglobin and Hematocrit levels would indicate abnormalities of the Red Blood Cells size. For example, a patient with a 12g/dl Hemoglobin level and %45 Hematocrit level (Increased volume) may suffer from abnormally large Red Blood Cells. Physicians however, don’t rely on this relationship to diagnose abnormality in the size of Red Blood Cells, instead they rely on the Red Cells Distribution Test (RCDT Blood Test) to gather more precise information about the Red Blood Cells size.

Hematocrit Normal Range

Hematocrit Normal Range varies between different age and sex groups. Males tend to have a %5 higher Hematocrit Normal Range than females. The Hematocrit Normal Range for males is between 42% and %52 while the Hematocrit Normal Range for females is between 37% and 47%.

Pregnant Females normally have a Low Hematocrit Level compared to the regular female’s Hematocrit Normal Range. Pregnancy normally cause physiological changes to females including an increased level of the female’s body fluids. Those increased body fluids involve an increase in the total body blood volume; a normal condition known as Chronic Hemodilution. Due to the increase in total blood volume, the volume of packed Red Blood Cells in a centrifuged tube will be relatively fewer than the regular levels. The Normal Hematocrit Level for pregnant females is less than 33%.

Newborns have the highest Hematocrit Normal Range; Hematocrit Levels normally decrease as the person ages. However, the Hematocrit Levels slightly increase during adolescence, and the Hematocrit Level may slightly decrease for elderly people.

The following is a listing of the Hematocrit Normal Range of children and adolescents where the Normal Hematocrit Levels tend to change in a faster rate the child grows:

  • Newborn: 44% to 64%
  • 2 to 8 weeks: 39% to 59%
  • 2 to 6 months: 35% to 50%
  • 6 to 12 months: 29% to 43%
  • 1 to 6 years: 30% to 40%
  • 6 to 18 years: %32 to 44%