Complete blood count with formula: normal, high and low values

Complete blood count with formula

What is the blood count?

The term blood count is the commonly used abbreviation for blood count. The latter is a exam of routine which is carried out on a blood sample of a person whose values of some important constituent components of the blood same.

L'blood exam completed with leukocyte formula it is carried out in many different circumstances, both in the pathological field and in normal conditions, both in hospital and outpatient practice, as it is able, through the interpretation of values by properly trained health personnel, to give countless clues regarding the state of health of a person or regarding the evolution of a possible pathology from which a person is affected.

What is the blood count and what does it measure

L'performing a complete blood count serves so that the doctor, or other healthcare personnel, can examine some values that indicate the status of those that are the activities of hematopoiesis (production of blood cells), of immune activity, and other specific activities of each organ of which it is composed. 'they are human.

In fact, many types of molecules and cells are poured into the blood, the concentration of which is closely linked to the activity of a specific organ: through the study of these values it is possible to understand the functionality of that organ and act. Consequently.

The values that are examined in the context of a blood count are numerous and we can distinguish some measurements that are performed consistently in each blood count and other measurements that do not always need to be investigated and are therefore at the discretion of the doctor who prescribes the complete blood tests .

How to read the blood count?

Within the group of values always reported in a blood count, there are parameters that describe some important characteristics of the main determinants of the part corpusculate of the blood, namely red blood cells, platelets and white blood cells:

  • Values that indicate the concentrations and production activity of red blood cells and their hemoglobin content: red blood cells (or erythrocytes), hemoglobin (Hb or Hgb), hematocrit, mean corpuscular volume (MCV), mean cellular hemoglobin content (MCH), mean cellular hemoglobin concentration (MCHC), red blood cell distribution width (RDW); the abbreviations in brackets are often reported in reports.
  • Values indicating platelet concentrations and production activity: platelet count and mean platelet volume (MPV, not always reported).
  • Concentrations and production of white blood cells, with the so-called "leukocyte formula": total leukocytes (white blood cells), neutrophils, eosinophils, monocytes, basophils and lymphocytes. All of these values except total leukocytes are usually reported in both absolute concentration and relative concentration to total.

In addition to these, other investigations may be required, usually aimed at resolving a suspected diagnosis that the doctor has towards the individual; some examples may be: values that investigate the state of iron in the blood or sideremia (ferritin, transferrin saturation, sideremia), the concentration of reticulocytes (precursors of the red blood cell, whose value indicates the state of proliferation and regeneration of the erythrocytes themselves), dosage of vitamin B12, vitamin D, liver enzymes (ALT, AST, etc.), plasma protein concentration and so on. All these investigations are not properly part of the complete blood count with leukocyte formula but are requested, and therefore reported, coinciding with this.

Complete blood count

Hematopoietic cells with precursors and end product of hematopoiesis, which is measured in the main blood test, the complete blood count.

When it is indicated to do the blood count

The request for a blood count can be made by the doctor with different intentions: in the form of a normal check to verify the health of the individual or his internal organs, in the suspicion of some alterations in the cell count or other components of the blood or finally to check response to therapy.

Therefore, the execution of a blood count is very frequent and is carried out on subjects of any age to check their state of health and direct any therapy.

Normal blood count values

How do you read the blood count? Here's how to read the blood count, remembering to always rely on the attending physician

The normal, high and low values of each of the parameters that are normally reported within the proper blood count will be discussed below. For the parameters requested separately, please refer to the other articles on the site.

It should be noted that the values shown below are theoretical, and that every laboratory in which analyzes are carried out has slightly different intervals on the basis of the technologies used and the average population sample of the territory they serve. It is therefore always necessary to refer to the normal ranges that are necessarily reported in any blood count report. Furthermore, it is good to understand that the finding of a busted blood count must first be evaluated by the attending physician, as very often the alterations can be completely benign or can sometimes lead to suspicions of even important pathologies and for which it is good to promptly investigate the painting.


With hct or hematocrit we mean the percentage of volume occupied by red blood cells with respect to the total blood volume; white blood cells and platelets are not considered, quantitatively much less important. Sometimes, erroneously, this value (and the values of red blood cells and hemoglobin) is referred to using the generic term "blood count": the terms low blood count and high blood count are therefore usually used when values related to erythrocytes are found that they tend to be low or high.

Normal values

In males, the reference values are between 39 and 50%, slightly lower in females, between 36 and 47%.

High values

An increase in the hematocrit value may correspond to a decrease in the liquid part of the blood (for example in the case of dehydration) or an increase in the corpuscular part (or red blood cells; for example in the case of polycythemia vera, stay at high altitudes, misuse of erythropoietin).

Low values

Finding values below the norm may suggest an excess of the liquid part (pregnancy, athletes) or a defect in the corpuscular part (anemia due to iron deficiency, vitamin B12 or folic acid, hemolytic anemia, chronic kidney disease, from leukemia, etc.).

Red blood cells or erythrocytes

The red blood cells (RBC) present in the blood play the essential role of carrying oxygen from the air of the lungs to the cells of all tissues and the reverse transport of carbon dioxide; these functions are carried out thanks to the hemoglobin content that characterizes the erythrocytes.

Normal values

The reference values of the concentration of red blood cells are different among men (4.5 - 5.9 106/ mm3) and the female one (4.0 - 5.5 106/ mm3), and change based on genetics, age, diet, level of physical activity, smoking habit, altitude, etc.

The reference values may differ according to the laboratory.

High and low values

Since the changes in red blood cells and hemoglobin follow the same pattern (as long as the MCH value, mean cellular hemoglobin content, is normal; see below), please refer to the paragraphs on high and low hemoglobin values.


Hemoglobin is a protein involved in the transport of oxygen within the blood, with the aim of carrying it to the tissues that are supplied by the bloodstream. It is one of the most important proteins within the human body, which however can undergo variations both in excess and in defects.

Normal values and factors affecting them

The normal range of hemoglobin values is different for males (13 - 17 g / dL) and females (12 - 16 g / dL), and is also conditioned by all those factors that are also valid for blood cell values reds.

High values: possible causes and consequences

Elevated hemoglobin values are actually defined erythrocytosis or polyglobulia, as they may be due to an increase in the number of red blood cells (erythrocytes) and not directly to an increased production of hemoglobin.

This alteration may be due to causes related to a lower concentration of oxygen in the inhaled air (in smokers, in the high mountains, etc.) or to defects in thehematopoiesis with real and proper haematological diseases (such as polycythemia vera); both of these two cases are defined as erythrocytosis absolute, that is due to a real increase in the erythrocyte mass). High values can also, more simply, be linked to a reduction in plasma volume (erythrocytosis relative, as the erythrocyte mass would be normal but has a higher concentration because the fluids have decreased).

In all these cases, in addition to hemoglobin, they will also be increased L'hematocrit and the concentration of red blood cells.

Elevated hemoglobin levels, unless they reach values extremely outside the normal range (which can cause headache, thrombosis, etc.), are unlikely to cause symptoms. Usually, the symptoms are linked to any underlying disease that also causes erythrocytosis.

Low values: possible causes and consequences

In the case of finding low hemoglobin, we speak of anemia, which can have many different causes and is quite common among both young individuals (especially women) and elderly individuals. The causes of anemias are essentially linked to everything involved in the maturation and synthesis process of red blood cells and hemoglobin (iron, vitamin B12 or folate deficiency, chronic diseases), as well as problems of destruction or loss of red blood cells themselves (hemolytic anemia, hemorrhages).

The most common form of anemia is linked to iron deficiency (iron deficiency anemia), especially attributable to a deficit in dietary intake and / or bleeding (for example through menstruation or gastrointestinal micro bleeding). One in four women in Europe have iron deficiency anemia, often unknowingly.

The consequences of an anemic state are manifold

In addition to the hemoglobin value that defines it, the values of MCV (mean corpuscular volume) and MCH (mean hemoglobin content) are of great importance in evaluating anemia.

MCV: mean corpuscular volume

This parameter defines the average size of red blood cells in the blood, defined as volume in femto liters (fL), or 10-15 liters (one millionth of a billionth of a liter).

The MCV value is of great importance for the more specific interpretation of the type of anemia that can be found from the hemoglobin value, as some types of anemia, depending on the underlying cause, present with an erythrocyte volume greater or less. We therefore speak of microcytic (if low MCV), normocytic (if normal MCV) or macrocytic (if high MCV) anemia.

Normal values

The range of values for mean corpuscular volume is 80 - 100 fL, or sometimes 83 - 97 fL. This range is quite reliable in any age group and in both genders.

There are many types of anemia associated with normal CVD values.

High values: possible causes

Generally, high values of MCV in the presence of low values of hemoglobin (macrocytic anemia or megaloblastic anemia) are associated with folic acid or vitamin B12 deficiency. Other, rarer conditions may be aplastic anemia (only in some cases), anemia due to myelodysplastic syndromes (part) or haemolytic anemia (some cases). The finding of macrocytosis of the red blood cells is therefore extremely useful in the clinical setting of the patient.

Low values: possible causes

In the case of microcytosis of the red blood cells it is good to evaluate the degree of lowering of the MCV value: a low grade microcytosis (MCV values between 75 and 80) are associated, in the vast majority of cases, with iron deficiency (especially between young women) or chronic disease (especially in the elderly); very low values of MCV (below 75, up to 55 fL) are instead more often associated with thalassemic syndromes (Mediterranean anemia and others; they are due to an altered synthesis of the protein chains that make up the hemoglobin molecule, and are essentially hereditary).

MCH: average cellular hemoglobin content

The MCH value reflects the average value of the absolute quantity of hemoglobin molecules within the individual red blood cells.

On the basis of the MCH it is possible to better define any anemia: we speak of hypochromic (with low MCH), normochromic (normal MCH) or hyperchromic (high MCH; this term has however fallen into disuse as it is not very informative). However, the MCV value is almost always sufficient to define the suspected cause of the anemia (further, more targeted tests are required), and the MCH value adds little information.

Normal values

The range of values considered normal for the mean hemoglobin content in erythrocytes is between 26 and 32 µg (picograms); this range may differ depending on the method used in the analysis laboratory and on the reference population.

Most anemias are normochromic.

High values

Higher than normal values are hardly observed, and are usually linked to megaloblastic anemia due to folate or vitamin B12 deficiency (in which it is almost the norm, however, to observe an increase in the MCV, which is therefore a more indicative parameter).

Low values

Hypochromic anemias are usually due to iron deficiency or chronic disease and are frequently associated with low MCV values (microcytic and hypochromic anemias); other associated pathologies can be sideroblastic anemias.

In chronic diseases, the reduction of these two values usually occurs if the chronic disease has been present for a long time, while initially it can present normocytic and normochromic.

MCHC: mean cellular concentration of hemoglobin

This value is obtained from the ratio between the value of MCH and that of MCV (MCH / MCV) with the correct units of measurement g / dL. It therefore represents the average concentration of hemoglobin within the individual red blood cells.

Normal values

Usually, this parameter is between 32 and 36 g / dL; also in this case it is possible to find differences in the reference values provided by the analysis laboratories.

High values

A high MCHC is found in conditions of spherocytosis (inherited or secondary to haemolytic anemia) or in hemoglobinopathies of type S or C.

Low values

A low MCHC can be associated with sideroblastic anemias (pathologies due to defects in the synthesis of heme, a fundamental component of hemoglobin) or with other types of hypochromic anemia.

RDW: distribution width of erythrocyte volumes

This value indicates the standard deviation (SD) of the MCV value, expressed as a percentage of the MCV itself; therefore, it indicates, in a simplistic way, the average percentage of variation of the MCV values around the average value.

Normal values

The reference values are 11.5 - 14.5%; therefore, on average, erythrocytes have a volume up to 14.5% larger or smaller than the reported MCV value.

These values vary very little according to the patient's age and gender.

High values

High RDW values indicate that there are very large erythrocytes and very small erythrocytes compared to the average. High values are therefore found already in the early stages of nutritional deficiency anemias (iron, folate or vitamin B12) or in some thalassemias, and help to differentiate these forms from other types of anemia in which normal RDW values are found.

Low values

There is no lower than normal values.

Platelets or thrombocytes

Plt or platelets are one of the fundamental participants in the process of wound healing and blocking bleeding, and it is therefore necessary to always evaluate their values.

Normal values

The concentration of platelets is usually between 100 and 400 thousand per cubic millimeter of blood (103/ mm3).

High values

The condition of high platelet values is defined as thrombocytosis or platelets (high platelets); it can depend on chronic diseases (in which the inflammation factors induce an increase in platelets), or it can depend on some pathologies such as polycythemia vera or essential thrombocythemia.

Low values

This is called thrombocytopenia or thrombocytopenia (low platelets); a low concentration of the number of platelets may be due to a lack of production (myelodysplastic syndromes, some leukemias, bone marrow aplasia, megaloblastic anemia, etc.) or to their destruction (autoimmune thrombocytopenia, often underdiagnosed).

White blood cells or leukocytes

White blood cells (WBCs) are among the main proponents of the human body's immune defense. They are divided into various subclasses, defined on the basis of microscopic appearance and function. In each blood count is reported the leukocyte formula, that is the distinction of the various leukocytes and the absolute and relative concentration of each of the classes. Leukocyte subtypes are granulocytes (neutrophils, eosinophils, basophils), lymphocytes and monocytes.

The condition of low levels of leukocytes is called leukopenia (leukocytes - low white blood cells), while the opposite picture is that of leukocytosis (leukocytes - high white blood cells).

Normal values

In the vast majority of the population, the concentration of leukocytes is between 4 and 11 thousand per cubic millimeter of blood (103/ mm3).

A normal leukocyte formula includes: neutrophils between 1.5 and 6.5 (45 - 70%), eosinophils between 0.10 and 0.80 (1 - 3%), basophils between 0.01 and 0.20 (0 - 1%) , lymphocytes between 1.20 and 3.40 (20 - 40%) and monocytes between 0.30 and 0.60 (3 - 7%).

For explanations on what are leukocytes, what are monocytes and other subclasses of white blood cells, please refer to the other sections of the site.

High values

The finding of elevated leukocytes (defined leukocytosis) is usually also defined on the basis of the relative prevalence of one of the leukocyte subtypes over the total, and we can therefore speak of leukocytosis neutrophilic (relative prevalence of neutrophils) or lymphocytic or lymphomonocyte leukocytosis (relative prevalence of lymphocytes or lymphocytes and monocytes). There is never an increase in eosinophils or basophils such as to lead to leukocytosis, as their concentrations are low; the conditions of relative prevalence of these two subtypes are therefore defined eosinophilia (in the absence of leukocytosis) e basophilia.

Normal leukocytes may be found together with neutrophilia (high neutrophils), neutropenia (low neutrophils), lymphocytosis (high lymphocytes) or lymphopenia (low lymphocytes).

Neutrophilic leukocytosis is a very frequent index of infection, especially bacterial ones; lymphomonocyte leukocytosis is found in some viral infections; eosinophilia can be found in the case of hypersensitivity (eg allergies) or in neoplastic haematological diseases; basophilia is usually associated with hypersensitivity, rheumatoid arthritis or neoplastic diseases (chronic myeloid leukemia, myelodysplastic syndromes).

Low values

Leukocyte levels of less than 4000 cells per cubic millimeter are usually associated with drug-induced immunosuppression, haematological cancer, or HIV infection.

Other values included in the blood count analysis

Platelet distribution width (PDW), mean platelet volume (MPV) and hemoglobin distribution width (HDW) values are rarely reported in blood tests; a high MPV indicates increased platelet production activity (“young” platelets are larger), while a low MPV indicates poor platelet production activity.

and Blood counts in pregnancy

Blood tests during pregnancy are extremely important on a regular basis to investigate any changes related to possible bleeding, immune reactions, or hormonal problems.

There is no danger in having a blood count with formula during pregnancy.

Cost of complete blood count

In a private regime, a blood count with a leukocyte formula can cost from 11 to 20 euros; under the SSN National Health Service it can be completely free or upon payment of a regionally defined ticket.

What does the complete blood count include? Different structures will provide all the values reported in the article, including the leukocyte formula and platelets; upon request, other common measurements can also be included (glycaemia, lipids, triglycerides, proteins, etc.)

Is fasting necessary?

Fasting is only required when, together with the blood count, tests are carried out concerning blood glucose (glycaemia) or fats (cholesterol, triglycerides). It is therefore not necessary, for a simple complete blood count with formula, to ask the healthcare professional what to eat.

How is the blood count performed? Here's how the test is done

To perform a blood count, only a normal blood sample is required: a nurse will identify the vein, disinfect the sample area and prick with a fine needle; very small amount of blood is sufficient.

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