Fasting Blood Test: Why?
Blood tests are among the most common medical tests, as they provide a lot of information about a person’s health status. For this reason, it is considered a basic routine test for almost all medical procedures.
They allow you to analyze several parameters, which is why they are prescribed when the presence of a disorder is suspected. The doctor will compare the values with the reference parameters. For example, blood glucose levels or the blood count, which measures the amount of cells in the blood.
Blood tests are preferably performed early in the morning and on an empty stomach, i.e. without having eaten or drunk anything in the last eight hours. In this article we explain why.
What are blood tests used for?
A blood test consists of taking a sample of blood from the individual and subsequent analysis in the laboratory. It allows you to examine different values in order to obtain information on the state of general health or on a particular organ.
In the second case, for example, the blood count is useful. This test measures the concentration of each type of blood cell in the blood, namely red blood cells, white blood cells and platelets. In addition to that, it shows the shape of these cells to evaluate possible abnormalities.
Likewise, many other biochemical values can be monitored, such as blood glucose or iron concentration. This group includes the parameters of cholesterol, triglycerides, thyroid enzymes, urea, etc.
All these parameters are essential for identifying certain pathologies : the values of thyroid enzymes can reveal a thyroid disease, while those of iron and other related elements help to evaluate a picture of anemia.
Blood tests may also be ordered when a tumor is suspected. During its development, it actually releases specific substances into the bloodstream.
Why is it important to fast before blood tests?
It is recommended that you have a fasting blood draw. This means that in the previous 8 hours, or throughout the night, you should not eat or drink anything (except water). This is because food and drinks are absorbed into the blood and can alter some parameters.
However, fasting is relative and depends on the parameter you want to analyze. In the case of a complete blood count, it is not necessary to fast. To evaluate the glycemic values, however, it is necessary to fast for at least 8 hours in the case of adults and at least 3 in children.
On the other hand, a 4-hour fast is sufficient for thyroid values. For cholesterol levels it is advisable to fast for about 12 hours. Another important aspect to consider is the effect of some medications.
In fact, like food, some medicines can alter blood values. Your doctor is aware of this, and may request that you stop taking the drug before the exam.
Other factors to consider
To ensure maximum reliability of the medical examination, healthcare professionals tend to make additional recommendations to the patient. In addition to fasting, smoking should be avoided just before the test. It appears that smoking can also alter blood sugar.
You can drink water, but in moderation, just to get enough hydration. On the other hand, it is completely contraindicated to drink alcohol before blood tests. It is also not recommended to do physical activity the day before, as it can alter some parameters.
In any case, the doctor will offer individual consultation. As already mentioned, each patient has different conditions, such as the need to stop some drugs or not, and can adapt the fast according to the values to be examined.
