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Morphology, ESR, cholesterol, and sugar are the most common blood tests. What else can a blood test show? How to prepare for research to avoid false results? It is not enough to register for an examination on an empty stomach.

Do I need to prepare for a blood test? It turns out that it is.

- Every few years I do periodic examinations at work - says 33-year-old Joanna, who works as a computer graphic artist. - The last ones turned out badly, although I prepared myself well for the research. On the day of blood collection, I did not eat breakfast, I did not even drink anything, and yet my results, especially cholesterol and triglycerides levels, were found by the doctor to be alarmingly high.

The previous ones were good, so why this sudden deterioration? Is this the beginning of atherosclerosis? In a month I did another blood test - the results were normal. Another repetition of the tests confirmed that everything is fine.

Why did this happen? Why did the first analyzes reveal a significant increase in blood cholesterol levels? Before we answer that question, let's see what could lead to false blood tests.

Blood tests should be done on an empty stomach

What you eat affects your blood picture and can distort your results. Especially the abundance and quality of recent pre-sampling meals.

Therefore, it is best to do blood tests on an empty stomach. But this is not always enough. If you analyze the level of glucose, cholesterol, triglycerides or leukocytes the day before, you should refrain from eating fatty and sweet foods, including drinking alcohol.

It cannot be less than 8 hours since your last meal. Before going to the lab, however, you can drink a glass of boiled water.

Why is the blood test done in the morning?

The physiological changes that take place in the body are subordinated to the circadian rhythms. The assessment of the influence of the time of day on physiology is the subject of chronopharmacology.

It shows, among others, that the concentration of sodium, potassium and magnesium ions - elements important for the functioning of the body - is lower at night and highest in the morning.

Phosphates (important for the flexibility of cells) are the most abundant at night, and in the morning they are very low. Creatinine, the content of which in the blood indicates the condition of the kidneys, rises in the evening.

However, the level of glucose, important for people who are at risk or alreadyin diabetics, it rises at night and falls during the day. Therefore, in each of these cases, it is best to donate blood for testing in the morning.

Similarly, the level of iron: it should be assessed on the basis of a sample taken in the morning, because in the afternoon the concentration of this element in the blood is the highest.

Also, the assessment of hemoglobin, without which the absorption of calcium and iron is difficult, will be the most objective in the hours when it is high. But, for example, in the case of thyroid and sex hormone determinations, the time of blood collection has no effect on the test results.

Read also: Blood morphology - with or without a smear? Norms and results of morphology

Important

Why did Joanna have bad cholesterol and triglyceride results?

In the evening she was at a meeting with friends. She didn't drink much wine, but she ate the Baked Knuckle and many other delicacies without hesitation.

She also did not despise the wonderful dessert. The excess calories, and above all fat and sugar, had to be stored somewhere. The insulin produced by the body was the first to deal with the excess sugar.

Much of this energy fuel was captured by the liver and some fat cells.

Even so, there were still too many cholesterol particles in Joanna's blood. The blood taken for testing was saturated with it, which was reflected in significantly elevated cholesterol levels - over 240 mg / dl.

If Joanna had done her tests 2 days after a sumptuous dinner, she would have had exemplary results corresponding to the actual state of her he alth.

Do you take any medications before the blood test?

If you are constantly taking medications, eg for high blood pressure, take them as usual. The doctor who guides us will be able to assess their influence on the results. If you must not take the drug before the examination, the doctor will inform you about it.

This is the most common procedure for determining the level of thyroid hormones. When you take, for example, vitamin and mineral sets without consulting your doctor, you must stop taking them 3-4 days before blood sampling. Otherwise, the so-called peak, i.e. a temporary high concentration of elements which mask their true level.

People who constantly take preparations containing iron should be especially careful. If you swallow a pill in the morning and donate blood after an hour or two, your iron levels will temporarily be at a good level.

Only after 3-4 hours it may drop below normal. Therefore, the doctor will not diagnose anemia. Before the examination, also stop taking herbal preparations, because, like synthetic drugs, they affect the activity of enzymes, hormonal balance andthe concentration of elements in the blood.

Read also: What can falsify test results?

What does a blood test look like?

The blood for testing is most often drawn from a vein in the elbow flexion, but you can also collect it from the vein on the back of your hand or foot. Needles of different thicknesses are used for this, and they are connected to special blood containers.

Before the needle is inserted, a tourniquet, i.e. a tourniquet, is put on and the place from which blood will be collected is disinfected. The containers with blood are sent to the laboratory, where a specialist examines the blood, assessing its composition and structure of blood cells under a microscope. Blood can also be tested automatically in a special analyzer. It is then a computer assessment of the composition of the blood sample.

What affects blood test results?

If the results are to be as close to the truth as possible, you need to know what else affects the concentration of various substances in the blood.

  • Ammonia- high levels may be the result of a large dose of alcohol in the evening or the use of painkillers.
  • Bilirubin- rises after alcohol, barbiturates, large doses of vitamin C.
  • Blood clotting time- longer after taking salicylates (such as polopyrin, aspirin).
  • Glucose(sugar) in the blood is lowered by high doses of vitamin C, alcohol, salicylates, steroids, caffeine, cigarettes, diuretics and psychotropics.
  • Thyroid hormones- their higher concentration is influenced by preparations containing iodine, corticosteroids, but also popular aspirin or polopyrin.
  • Iodine - elevated levels are sometimes the result of taking oral contraceptives, thyroid hormones, testosterone, and acetylsalicylic acid.
  • Uric acidwill be lower than it actually is after alcohol and cold medications.
  • Lipids and cholesterol- their levels will increase significantly after a fat evening meal, and lower after alcohol and antibiotics.
  • Magnesium- its concentration decreases after the abuse of alcohol, coffee, oral contraceptives. However, it grows with high doses of calcium and vitamin D3.
  • Potassium- the level drops after diuretics.
  • Prolactin- its concentration increases with alcohol and regular use of oral contraceptives.
  • Liver tests(ALT transaminases, AST) - results may be increased by painkillers, anti-inflammatory drugs, sulfa drugs, antibiotics, anabolic steroids, as well as high doses of vitamin C.

With blood test results todoctor

After the blood test, you get a printout from the laboratory with test symbols. Next to it are the standards, usually in the range from - to. If the result is within these limits, then everything is fine.

The average of the analysis results was adopted as the norm in 95%. completely he althy people. The results deviating from the established norm can be achieved by a completely he althy person, because this is - as they say - her beauty.

This is often the case with higher cholesterol (up to 220) and triglycerides, but before you can be sure it is, the tests must be repeated many times, while maintaining a dietary regime.

Standards provided by laboratories may differ from each other. This is the result of using different methods of determining blood components. Therefore, you must not judge the results yourself. In fact, only a doctor can interpret them.

Read also: CRP - when is CRP performed? What are the CRP standards?

When should I have a blood test?

  • You're taking painkillers. Their main ingredients - paracetamol or ibuprofen - may overload the liver with prolonged and frequent use (AST, ALT tests).
  • It breaks your bones. This could be a sign of inflammation or rheumatic disease (blood test, ESR).
  • Your hair is falling out, you are constantly tired. You may find that you are iron deficient or have low hemoglobin levels and not enough red blood cells (general blood test, iron levels).
  • You are overweight. Check that you are not at risk of coronary heart disease or suffer from hypothyroidism (blood test with total cholesterol, LDL, HDL, triglycerides, and hormones - TSH, T3 and T4).
  • You are losing weight quickly. Weight loss may indicate an overactive thyroid gland or cancer (TSH, T3 and T4 tests and morphology).
  • You have a thirst. If you are constantly thirsty, you may have diabetes (blood sugar tests and ESR) or hyperthyroidism (TSH).
  • You have bruises all the time. They are formed when blood clotting is low, but can also signal diabetes (blood clotting time and sugar level tests).
  • You like strong alcohol. Alcohol, especially in excess, damages the liver (determination of the level of the gamma GTP enzyme in the blood)

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