Looking after your health is a process that involves a number of elements - one of which may be well-chosen supplementation. It is worth preparing for this so that you don't take specific products "blindly" without realising how they actually affect your body. In this case, laboratory tests may be helpful in order to learn more about your condition and detect possible abnormalities or deficiencies in time. Not sure what tests you should perform? Check out this list of basic diagnostic tests, which you should definitely go for once a year.

What tests should be carried out regularly?

At the outset, it is worth pointing out that there is no universal set of tests that will work in every case. There are, however, several parameters that are good preventive tools and which, in the event of deviations from the norm, allow the specialist to order other, more extensive tests. Basic laboratory tests are therefore a good starting point for further diagnosis and are worth performing at least once a year. These include:

• blood count; 
• glycaemia;
• lipidogram;
• testing of vitamin D levels; 
• CRP;
• liver tests;
• general urine examination.

What do the results of each study tell us?

Blood morphology

One of the best known and most frequently performed blood tests is the blood count. Doctors order it both as a preventive measure and in the event of a patient's ill health. Abnormal results of individual blood count parameters are the first warning sign on the basis of which a specific treatment is selected or diagnosis is deepened.

The main components of blood are the plasma (the fluid that surrounds the blood cells) and the morphotic elements, or blood cells - these include red cells, white cells and platelets. Morphology is a test that assesses the quantity and quality of the listed blood components. Its basic indicators include:

• red blood cell (RBC) count;
• white blood cell count (WBC);
• platelet count (PLT) ^[1].

Red blood cells (erythrocytes) transport oxygen from the lungs to the body's tissues, where it is exchanged for carbon dioxide. Haemoglobin, which is contained in erythrocytes, is responsible for these functions. Based on the analysis of red blood cell levels, it is possible to diagnose, among other things, anaemia, which manifests itself as a drop in erythrocyte or haemoglobin levels ^{[2, 3]}. White blood cells (leukocytes) play an important role in the normal course of immune processes by protecting the body against infections ^[4]. Platelets (thrombocytes), on the other hand, participate in homeostasis (i.e. maintaining the body's equilibrium) and blood clotting, and also influence immune function ^[5].

In this examination, it is also important to determine the haemoglobin concentration and haematocrit values, from which it is possible to determine the erythrocytic indices: mean red cell volume (MCV), mean haemoglobin mass per cell (MCH) and mean haemoglobin concentration per cell (MCHC). By performing a blood count, we can also know the number and percentage of the five types of white blood cells, which include neutrophils, lymphocytes, monocytes, eosinophils, basophils ^[1].

Testing fasting glucose levels

Blood glucose testing can diagnose diabetes and pre-diabetic conditions. Given that the symptoms of diabetes remain latent for many years, the importance of regular testing is crucial. Glucose testing is particularly important for those at risk of developing diabetes. Risk factors include genetic load, overweight, hypertension, sedentary lifestyle, upper body obesity (refers mainly to waist measurements). Symptoms of type 2 diabetes that should attract particular attention include: increased thirst (which also results in increased urine output), dry mouth, fatigue, anxiety, recurrent infections and decreased vision (which can be seen in the advanced stages of the condition and is a complication of untreated diabetes) ^[6].

Lipidogram

The lipid profile assesses the risk of cardiovascular diseases. The following parameters are determined in this study:

• Total cholesterol (CHOL) - serves as an indicator of the presence of lipid disorders and is essential for calculating LDL cholesterol and non-LDL cholesterol ^[7];
• HDL cholesterol (high-density lipoproteins) - commonly referred to as the 'good cholesterol'; the main role of HDL is to transport cholesterol molecules from tissues to the liver, where cholesterol is metabolised; it has anti-atherosclerotic effects influenced by, among other things.among others, anti-inflammatory, antioxidant, anticoagulant and profibrinolytic (i.e. facilitating the dissolution of thrombi) functions [8]; low levels of high-density lipoprotein increase the risk of cardiovascular disease ^[9];
• LDL cholesterol (low-density lipoprotein) - commonly referred to as 'bad cholesterol'; it has a vasoconstrictive effect - it affects the deposition of cholesterol particles in the walls of arteries, narrowing their lumen, which impedes the flow of blood and oxygen, and also has pro-inflammatory and clot-forming properties [10]; high levels increase the risk of cardiovascular disease ^[11];
• Non-HDL cholesterol - this is calculated by subtracting HDL values from total cholesterol; it reflects the levels of all cholesterol fractions with atherosclerotic effects ^[12]; 
• Triglycerides (TGs) - have an insulating and energy-saving function in adipose tissue; their high levels are associated with arteriosclerosis and increased risk of cardiovascular disease ^{[13, 14]}.

Testing of vitamin D levels

Vitamin D is involved in calcium and phosphate metabolism and influences the smooth functioning of the immune system. Deficiencies of the so-called sunshine vitamin are very common. This is due to the fact that the best source of it is skin synthesis - this requires being in the sun for about 5-30 minutes between 10am and 4pm with face, arms, hands and legs uncovered ^[15]. As it is not easy to have this practice (especially in cold weather), many people support themselves with supplementation. It is worth remembering that it should be selected by a specialist. A blood test of vitamin D levels may be helpful for a doctor or dietician to determine the recommended intake.

CRP

C-reactive protein, or acute-phase protein, is an indicator whose elevated levels may indicate ongoing inflammation (both chronic and acute), infections and infectious conditions in the body ^[16].

Liver tests

Liver function tests, liver function tests, commonly referred to as liver function tests (LFTs), are an effective method of detecting disorders of this organ. The liver plays a key role in metabolism, digestion, detoxification and elimination of substances from the body. The most commonly determined liver parameters include:

• ALAT, ALT (alanine aminotransferase),
• AspAT, AST (aspartate aminotransferase).

These indicators can help determine the area of liver damage ^{[17, 18]}.

General urine examination

A urine test is performed to assess general health. It can detect e.g. urological diseases (e.g. lithiasis, urinary tract infections), as well as systemic ailments. A complete urinalysis is based on physical (e.g. colour, clarity, density), chemical (e.g. reaction, presence of sugar, protein, ketone bodies or bile pigments) and microscopic tests ^[19].

How to prepare for the research?

The final result of the tests is influenced not only by the general condition of the body, but also by the appropriate preparation for the tests. What are the general recommendations? The person being tested should report to the point of collection:

• in the morning after a well-rested night's sleep,
• fasted (with an 8-12 hour break from eating),
• with at least a 24-hour break from alcohol, heavy and hearty meals and demanding physical activity.

It is worth remembering to remain at rest immediately before the examination and not to smoke. You are allowed to drink a small amount of water in the morning. Many medications and food supplements can affect the test results, so it is best to consult with your doctor as to whether you should stop taking them before performing diagnostic tests ^[1]. For urine testing, it is useful to read the instructions on how to collect samples correctly - urine is placed in a special container and collected immediately after a night's sleep from the midstream ^[20].

Remember that the results of the tests should be consulted with your doctor, who, on the basis of both the given parameters and your clinical symptoms, will choose the appropriate treatment or refer you for further diagnostics.

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