What is a blood test? | Medical tests

Analysis of blood

Blood test is a medical test used and most important in clinical practice. It consists of removing a small amount of blood from the patient, which is then transported to the laboratory to analyse and determine its composition.
In an analysis we can find numerous data, many of which can be ringing us Chinese given their acronyms and different figures. Then we will try to clarify what each of them, what are the normal levels and which indicate that something is altered in our body.
Which are most requested for the study are normally, the blood count and blood Biochemistry:
Blood count: is a quantitative study that evaluates the concentration of each of the cellular elements of the blood. Also check if cells have normal a form and structure or, conversely, are altered. Example: red blood cells (also called RBCs), white blood cells, neutrophils...
Biochemistry: is the study of chemical substances present in the blood. Examples: potassium, calcium, sodium, magnesium, vitamins, hormones...

Why can the doctor request a blood test?

Actually, the blood test is a test that can be requested for almost any medical consultation, in order to assess the general State of the patient. Along with its history, will serve to help the doctor to resolve two important issues: what happens to the patient and why it happens. An example: a person comes to consultation with remarkable tiredness, loss of appetite and pallor; in this case, a simple blood test can reveal itself a diagnosis: anemia, iron-deficiency (due to lack of iron). Thus, you can start now to treat your illness without need for further testing.
But we must bear in mind that the analysis of blood is not only a method to diagnose diseases, is also a way of controlling the State of the patient; for example, are made to patients undergoing chemotherapy routine Analytics to check the status of your immune system; and also before a hormonal treatment with oral contraceptives, it is important to know the level of hormones in the patient's blood.

Recommendations and preparation for the analysis of blood

The most important thing when you go to make you an blood test is go on fasting, to avoid the presence of factors that may give errors in the results. Blood is usually done in the morning, so from the midnight patient should be fasting (usually corresponds to a period of 8-10 hours).
It's a little painful test for most people, although some may feel some pain or discomfort when you click them or during the extraction of the blood. Sometimes the patient may get dizzy or even lose consciousness due to fear of the analysis or to prolonged fasting, but in any case this incident is related to the extraction, since the amount of blood that is collected is very small. In any case, if you are prone to motion sickness, it is advisable that it is accompanied to the test.
As the adverse effects of the implementation of the analytical, may be an small hematoma or swelling in the area of extraction. This is because the output of blood from the vein by the place where has clicked. Hematoma goes away in a few days without treatment.
The only contraindication to the realization of a blood test is the intake of anticoagulants. These drugs could cause higher than normal, or very extensive bruising bleeding.

How to interpret blood test results

The presence in the results of an analysis of one or more of the blood abnormalities that are detailed below does not necessarily mean that will suffer any of these diseases. A blood test is a test that is complementary to many others that must occur before obtaining a final diagnosis.
The patient must not worry before an descent or isolated elevation of any of the parameters mentioned, is the doctor who has to assess its meaning, within the context of the history, and in relation to other symptoms and to the personal circumstances of the patient (lifestyle, presence of other illnesses, medication that are taking...).

Normal results of a blood test

Below, we present a series of data that are usually reflected in a common blood analysis , along with the values estimated would be within the normal or healthy.
Normal values of a blood count
  • Red blood cells
  • Hemoglobin (Hb)
  • Hematocrit (HCT)
  • MCV (mean corpuscular volume)
  • MCH (mean corpuscular hemoglobin)
  • Lymphocytes
  • Leukocytes
  • Neutrophils
  • Eosinophils
  • Platelets
  • ESR (sedimentation rate)
  • Natural values
  • 4.5 – 5.9 million/mm3 in males
  • 4 - 5.2 million/mm3 in women
  • 13, 5-17, 5 g/dl in men
  • 12 - 16 g/dl in women
  • 41-53% in men
  • 36-46% in women
  • 88-100 fl
  • 27-33 PCs
  • 1,300-4,000 /mL
  • 4,500-11,500 mL
  • 2,000-7,500 /mL
  • 50-500 /mL
  • 150000-400000 / mm3
  • 0 - 10 mm/h for men
  • 0 - 20 mm/h in women
A biochemistry normal values
  • Glucose
  • Urea
  • Uric acid
  • Creatinine
  • Cholesterol
  • HDL
  • LDL
  • Triglycerides
  • Transaminases:
  • GOT
  • GPT
  • GGT
  • Alkaline phosphatase
  • Calcium
  • Iron
  • Potassium
  • Sodium
  • Bilirubin
  • 70 - 110 mg/dl
  • 0.6 - 1.5 mg/dl
  • 2 - 7 mg/dl
  • 70 - 110 ml/min
  • 120 - 200 mg/dl
  • 42 - 90 mg/dl
  • 0 - 160 mg/dl
  • 30 - 280 mg/dl in men
  • 30 - 220 mg/dl in women
  • 7-40 units/liter
  • 5-43 units/liter
  • 12-55 units/liter
  • 89-280 units/liter
  • 8.5 - 10.5 mg/dl
  • 50 - 150 mg/dl
  • 3.5-4.5 mmol/litre
  • 135-145 mmol/litre
  • 0.2 - 1 mg/dl

Results and values of a blood count

The complete blood count (CBC) will reflect all the elements or components of blood, their number and their proportion in the organism and if suffer alterations:
  • Red blood cells or red blood cells
  • Hemoglobin (Hb)
  • Henatocrito (OHT)
  • Mean corpuscular volume (MCV)
  • MCH (mean corpuscular hemoglobin)
  • Leukocytes or white blood cells
  • Platelets
  • ESR (sedimentation rate)
You know what indicates each value appeared in the results of a blood count, and what it means if your levels are high, low, or normal:
Known as red blood cells, are the most important blood cells, since they are responsible for transporting oxygen to the rest of the cells of the body.
  • Normal levels: 4,500,000-5.900.000 /ml in males
  • 4.000.000-5.200.000/ml women
  • Low levels: the number of red blood cells decreases significantly when there is bleeding (for example because of abundant menstruation), and this makes that not enough oxygen reaching the other cells of the body, which is what is known as anemia. All blood cells are produced in the bone marrow, so cell count failures may reflect a change at this level.
  • High levels: an increase in the number of red blood cells is known as poliglobulia; This process makes blood thicker than normal, which facilitates the formation of thrombi in the blood vessels inside. It can be of unknown cause or be due to an excessive Hyperfunction of the bone marrow.
  • Smoking reduces the amount of oxygen present in the blood, and this has resulted in an increase in the production of red blood cells, so a large number of red blood cells can also be related to smoking.
  • In general, to a decrease of oxygen in the blood, the body tends to respond by producing more red blood cells, by what people who live in high areas may present a greater number of red blood cells without implying that they suffer from any disease.
It is a protein made of iron, which is located in the interior of the erythrocyte, and who is responsible for the red color of blood. Each erythrocyte usually contains between 200 and 300 molecules of hemoglobin. It is thanks to hemoglobin oxygen and nutrients from reaching the rest of the body tissues. Also carries carbon dioxide to the lungs to be exhaled.
  • Normal levels: 13, 5-17, 5 g/dl in men.
  • 12 - 16 g/dl in women.
  • Low levels: as the amount of hemoglobin is proportional to the number of red blood cells (erythrocytes), a decline of this protein is reflected in an inefficiency of the function of red blood cells, which is called anemia.
  • High levels: the elevation of this protein may contribute to the emergence of poliglobulia, an increase in the number of red blood cells that can cause clots. High levels in people with heart disease, chronic lung problems or people who live in areas of high altitude may appear.
It is the volume of red blood cells in blood expressed as a percentage of total blood volume.
  • Normal level: 41-53% in men
  • 36-46% in women
  • Low levels: because, in reality, this parameter indicates the number of red blood cells, the main cause of a drop in hematocrit is anemia. Other reasons may be: bleeding, pregnancy, problems in the bone marrow, leukemia, hyperthyroidism...
  • High levels: increasing the level of hematocrit may be produced by cardiac problems, lack of hydration, chronic lung diseases...
Mean corpuscular volume (MCV)
This rate determines the average size of the red blood cells. Thus, the anemia can be classified in: / macrocytic or microciticas, depending on whether the size of the erythrocyte is larger or smaller than usual.
  • Normal level: 88-100 fL (femtolitros by erythrocyte).
  • High levels: high VCM (large red blood cells) may have its origin in a deficit of vitamin B12 or folic acid, disorders of the liver, or consumption of alcohol, and does not remain constant throughout life; in the newly born is high.
  • Low: can be caused by anemia or Thalassemia (alteration of hemoglobin).
MCH (mean corpuscular hemoglobin)
This parameter indicates the average amount of hemoglobin which contains each erythrocyte or red cell.
Thanks to this parameter anemias can be classified in a different way: the hipocromicas are those who are studying with a low level of HCM, and the hipercrómicas which have a high level of HCM.
  • Normal levels: between 27 and 33 PCs (picograms).
  • Low levels: the most common thing is that there is anemia due to lack of hemoglobin (normally by iron deficiency).
  • High levels: there are rare cases of hipercrómicas anemia. They can alert a deficit of vitamin B12 or folic acid.
White blood cellsare also called, and play a role in defense of the body against external aggressions. Due to this function, a low level of leukocytes predisposes the patient to suffer from infections.
There are several different types of leukocytes, which are explained below:
Lymphocytes: is a type of Leukocyte that lacks granules. They are very important cells in the immune system, since they are able to respond to agents unknown to the body.
  • Normal level: 1,300-4,000 /ml
  • High levels: the increase in the number of lymphocytes is known as Lymphocytosis. It appears in infectious acute, chronic, drug allergies and processes Lymphoproliferative Disorders such as leukemia.
  • Low levels: the decrease in the number of lymphocytes called lymphopenia, and it is common to find it in people whose immune system is defective or they are following treatment (chemotherapy) immunosuppressant.
Neutrophils: is a type of Leukocyte that contains granules, which is stained easily with dyes neutral. They are responsible for destroying bacteria, cell debris and solid particles.
  • Normal levels: 2,000-7,500 /ml
  • High levels: the high number of neutrophils (neutrophilia) appears before infections, inflammation, Burns, acute bleeding, smoking, and heat stroke. It may be associated with also processes in which the death of the cells of some tissue, such as myocardial infarction occurs.
  • Low levels: is called neutropenia to the decline in the number of neutrophils, which gives the patient a special vulnerability to infections, even the most insignificant.
Eosinophils: is a type of Leukocyte that presents many granules inside and stained with acid stains.
  • Normal: 50-500 /ml
  • High levels: Eosinophilia (increase in the number of these cells) may indicate the presence of parasites, allergies, asthma and infections. It is also associated with intestinal diseases such as Crohn's disease and celiac disease, and pulmonary diseases (Löffler).
  • Low levels: the decline in the number of eosinophils is rare.
They are the smallest elements of the blood, and are essential for blood clotting, since they are responsible for closing the blood vessels, causing blood to clot to plug the injury when there is a wound.
  • Normal levels: between 150.000-400.000/ mm3.
  • Low levels: lower than normal platelet count is what is known as thrombocytopenia. It may be due to an abnormal accumulation of platelets in the spleen or a bad function of the bone marrow. It has as a consequence poor blood clotting, resulting in bleeding (nose, gums, skin bruising, blood in urine and stool...). There is a disease of the immune system, the idiopathic thrombocytopenic purpura, which is characterized by the formation of antibodies that destroy platelets, failing to recognize them as their own body.
  • High levels: the high number of platelets in the blood, is called thrombocytosis, and can cause the formation of thrombi within the arteries. It can appear without just cause, as reaction before an acute bleeding or certain diseases, or because a spinal cord malfunction.
Globular (VSG) segmentation speed
This parameter measures the speed at which sediment red blood cells at a time (1-2 hours).
  • Normal levels: between 0 and 10 mm/hour in men and between 0 and 20 mm/h in women.
  • High levels: there are many processes that can be studied with an increase of the VSG, such as myeloma, lymphomas, leukemias, chronic inflammatory processes such as rheumatoid arthritis and lupus. But his elevation does not necessarily indicate a pathology, since it also rises in some physiological processes such as pregnancy, menstruation or in the elderly.
  • Low levels: ESR is usually rarely decreased. However, it is useful in the follow-up of patients data, since reducing ESR suggests that the tax treatment is being effective.
Results of a biochemical analysis
An analytical or biochemical routine analyzes the concentration in the organism of different chemical substances. Know what indicates each value that appears in the results of a biochemical analysis, and what indicates the fact that their levels are high, low, or normal:
  • Glucose
  • Urea
  • Uric acid
  • Creatinine
  • Cholesterol
  • Triglycerides
  • Transaminases
  • Alkaline phosphatase
  • Calcium
  • Iron
  • Potassium
  • Sodium
  • Bilirubin
It is a sugar found in many foods, especially fruits, and constitutes a fundamental source of energy for the human being. The analysis determines the amount of sugar present in the blood and serves to determine, for example, if you are suffering from diabetes or glucose intolerance (which sometimes means that the patient is in a situation of pre-diabetes).
  • Normal levels: 70 - 110 mg/dl
  • Low levels: hypoglycemia (low blood - below 50 mg/dl glucose-) causes dizziness, drowsiness, loss of consciousness, spasms, heart rate decreased and, in severe cases, can even reach the coma. May be due to a wide fasting period, a defect in the formation of insulin, such as pancreatic insufficiency, tumors, alcohol intake; either be hereditary cause. Diabetes patients can suffer this condition because of too much on medication used to correct your problem.
  • High levels: hyperglycemia (levels above 120 - 130 mg/dl) cause diabetes mellitus, which is usually hereditary. In these cases occurs increased food intake, blood vessels and peripheral nerve injuries. However, high levels can also indicate that there is glucose intolerance. Some medications and certain diseases (Cushing Syndrome, acute pancreatitis...) can raise levels of glucose.
It is the final product of the degradation of proteins, and is excreted in the urine. It is a measure that serves to check the correct functioning of the kidneys, the State of dehydration in a person and is even an indication of an alteration of the body mass.
  • Normal: 0.6 - 1.5 mg/dl
  • High levels: hyperuricemia, which is the elevation of that product, may be due to diets rich in proteins, to kidney failure, heart failure, bleeding or very prolonged fasting. Urea is also elevated in individuals who have high muscle mass. This increase may also be due to taking some medications that affect the kidneys, urinary calculi or tumor, by dehydration, or even when Burns have occurred in tissues.
  • Low levels: the hipouricemia, on the other hand, is due to diets poor in proteins, pregnancy, malnutrition or liver failure.
Uric acid
It is a waste product that results after the nitrogen metabolism in the human body, which is eliminated primarily in the urine.
  • Normal levels: 2 - 7 mg/dl
  • High levels: the main causes for that increase uric acid are figures: gout, renal lithiasis and kidney failure. Although it can also occur in cases of diabetes mellitus, and alcoholism. Frequently eating foods rich in protein such as seafood, spinach, blue fish and red meat also favors the increase of the level of uric acid. A high level after strenuous exercise may even appear.
  • Low levels: the descent of uric acid appears in some disease in the renal tubules (Fanconi syndrome) or very low protein diets.
It is a compound obtained from the degradation of creatine, which is one of the most useful for the muscles nutrients.
  • Normal levels: 70 - 110 ml/min
  • High levels: its increase is caused by dehydration, failure renal (for Glomerulonephritis or kidney stones), disorders of the urinary tract as the obstruction caused by a calculation or by increasing the size of the prostate, and is also seen in the early stages of muscle diseases (Dystrophies).
  • Low levels: his descent is seen in patients that have low muscle mass, and can also be caused by serious Muscular Dystrophies.
It is a substance found in the fats, oils, and egg yolk, and is widely distributed by the body (blood, liver, bile,...).
  • Normal levels: cholesterol (120 - 200 mg/dl); HDL (42 - 90 mg/dl), LDL (0 - 160 mg/dl)
  • High levels: the rise in cholesterol produces Xanthomas (yellow nodules that appear on the skin) and xanthelasmas (in this case the nodules appear around the eyes). When the value of cholesterol is normal (between 0 and 200 mg/dL), it means that the level of fat in the body is suitable, but if it is high it is necessary to analyze the two kinds of cholesterol (HDL and LDL), taking into account that the total cholesterol is the sum of the other two.
    • HDL: is the so-called 'good cholesterol'. It is a protein that is capable of transporting cholesterol from the inside of the arteries to the liver, where it will be metabolized.
      • High levels: this protein imply protection against the risk of serious cardiovascular disease, such as myocardial infarction.
      • Low levels: especially in women, are a risk factor for suffering episodes of cardiac ischemia.
    • LDL: this type of cholesterol can build up in the cells of the arterial wall, even to obstruct them.
      • High levels: the higher the level of this type of cholesterol, more likely to be heart disease due to arterial obstruction. Because of this risk, the optimum would be keep low levels of this cholesterol in the blood, and this is particularly important for those people who have already had a cardiovascular problem (in these cases recommended levels below 100 mg/dL).
It is a compound that is part of fats and vegetable oils, which accumulates in the body tissue adipose (is the fat that there are just under the skin). They are a good thermal insulator.
  • Normal levels: 30 - 280 mg/dl in men; 30 - 220 mg/dl in women
  • High levels: hypertriglyceridemia, as well as the increase in LDL cholesterol, is a factor of cardiovascular risk for atherosclerosis. People with a tendency to have high both parameters should be eliminated from your diet fat and oils, which are responsible for the increase of this parameter. There is another reason to have elevated the level of triglycerides, which is the familial hypertriglyceridemia, an inherited disorder. The consumption of alcohol or tobacco influences also have high triglycerides.
It's enzymes, whose value increased in blood may indicate liver damage. Obesity is a risk factor for accumulating fat in the liver, which can raise the level of transaminases, as well as having cysts or tumors, or a serious obstruction of the bile duct. There are three main types of transaminase:
  • GOT: is a key protein in the liver and the heart, which is released into the blood when these organs are altered.
    • Normal level: 7-40 units/liter.
    • High levels: the elevation of this protein will detail it in the next section, since both transaminase elevation tends to be linked.
  • GPT: is a protein that is found in large quantities in the liver and which, like the GOT rises when fails this organ.
    • Normal: 5-43 units/liter.
    • High levels: its elevation is caused by liver alterations, which may be mild (acute hepatitis or fatty liver), moderate (alcoholic hepatitis or paracetamol poisoning) or something more serious (chronic hepatitis).
  • GGT: like the rest of transaminases, is a protein that is released from the liver when there is an injury. This in particular is associated with alcohol intake.
    • Normal levels: 12-55 units/liter.
    • High levels: the causes of the GGT elevation are similar to the alkaline phosphatase: cholestasis intra and extra-hepaticas (either by tumor causes, or alcoholic cirrhosis).
Alkaline phosphatase
It is a protein responsible for bone mineralization, so it is mostly in the bone. The causes of their elevation are the same causing the elevation of GGT, which are detailed in the previous section. Its increase is also related to diseases of bone, such as infection or tumor infiltrations.
  • Normal level: 89-280 units/liter.
  • High: during growth, children usually have high numbers of alkaline phosphatase, as occurring after a bone fracture during the time in which the bone is recovering from the trauma.
  • Low levels: levels, however, decrease in cases of malnutrition.
It is an important chemical element for nerve transmission, muscle contraction, blood coagulation and cardiac function. Calcium is milk and derivatives, spinach, sardines, nuts, and white beans.
  • Normal levels: 8.5 - 10.5 mg/dl
  • High levels: hypercalcemia is often due to an excessive function of the parathyroid glands. Cause alterations of consciousness, anorexia, vomiting, constipation, heart arrhythmias and renal and biliary lithiasis.
  • Low levels: hypocalcemia, unlike that in the former case, is due to a hypofunction of the parathyroid glands, although also seen in cases of alcoholism and pancreatitis. In this case there may be grass tetany members and arrhythmias.
It is a fundamental chemical element in the structure of haemoglobin and, therefore, for the transport of oxygen to the rest of the body. Iron is found in: liver, red meats, nuts and dried fruits, legumes, green vegetables and cereals.
  • Normal: 50 - 150 mg/dl.
  • High levels: some diseases can cause a high level of iron in the body, such as hemochromatosis, which causes the body to absorb too much iron.
  • Low: the low level of iron in the blood makes hemoglobin may not form properly, therefore oxygen and nutrients fail correctly to the rest of the body tissues. This is called iron deficiency anemia, manifesting itself, like the rest of anemias, such as fatigue, muscular weakness, drowsiness and pallor.
It is an important element for neuromuscular transmission and muscle contraction, but especially involved in the regulation of the balance acid-base of the body. Potassium is found in: wheat, nuts, bananas, carrots, beets, potatoes and Avocados.
  • Normal level: 3.5-4.5 mmol/litre.
  • High levels: the increase of this element in blood is known as hyperkalemia. Its most important causes are: increased intake, decreased its elimination (renal failure), and hyperglycemia. It manifests clinically as heart arrhythmias, difficulty swallowing, and a feeling of numbness in hands and feet.
  • Low levels: hypokalemia is a lower level of potassium in the blood. The most frequent causes are: decreased intake, losses (vomiting, diarrhea and use of diuretics), hypothermia and hormonal changes (increase of insulin). It manifests itself as fatigue, muscle cramps, weakness and paralysis in very advanced States, intolerance to carbohydrate carbon and increase the risk of cardiac arrhythmias.
It is a chemical element that is very important to perform the same functions of potassium. It is present in the salt and cured meats.
  • Normal: 135-145 mmol/litre
  • High levels: hypernatremia is defined as a high level of sodium in the blood. This situation may be due to an increase in the intake of salt or to drink little water. The clinical manifestations are more serious mas rapid rises in blood sodium and tend to be: tremors, confusion, convulsions, and risk of brain bleeding.
  • Low levels: at the other end, the low level of sodium in blood is known as hyponatremia. It may be due to sodium loss (vomiting, diarrhea, excessive sweating...), excessive diuresis, or defects in the adrenal hormones. In these cases can appear clinic hypotension, tachycardia, ocular and cutaneous dryness and weight loss.
It is a substance that usually contain bile, resulting from the degradation of hemoglobin, and is yellowish. Indicates if the liver and bile duct work as they should.
  • Normal levels: 0.2 - 1 mg/dl.
  • High levels: the increase in bilirubin can be due to: hereditary disorders in the metabolism and elimination of this protein, alterations in the anatomy of the biliary or obstruction by stones in the gallbladder or liver disease (cirrhosis or hepatitis). If this substance greatly increases it will appear jaundice (yellowing of skin and mucous membranes) and dark urine (urine of dark, due to the urinary elimination of bilirubin).
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