Blood tests: how to prepare, when and where to perform, how to interpret the results?

Blood tests can detect many conditions, monitor treatment and also assess the patient's general condition.

AuthorLudwik Jelonek

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Ludwik Jelonek is the author of more than 2,500 texts published on leading portals. His content has found its way into services such as Ostrovit and Kobieta Onet. At Natu.Care, Ludwik educates people in the most important area of life - health.

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Reviewed byWitold Tomaszewski

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Reviewed byWitold Tomaszewski

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Doctor of Medicine, food and pharmaceutical law expert and experienced medical professional.

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Blood tests: how to prepare, when and where to perform, how to interpret the results?

10 July, 2024

17 min

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Blood tests allow us to check a patient's general condition, monitor treatment and also diagnose diseases. Most of us can perform them at a nearby clinic. Blood tests are not expensive, time-consuming or cumbersome.

Once a year. That's how often we celebrate a birthday or Christmas. So often we start the school year. But once a year we should be doing something else - having a preventive blood test. A few minutes spent on this diagnostic can help reveal a dangerous disease and increase the chance of a cure.

From this article you will learn:

Why and when to have blood tests
How to prepare for blood tests
What are the basic blood tests
How long are blood tests valid
How to interpret blood tests

If you notice some of the worrying symptoms described in this article contact a specialist at Tomorrow Medical or go for a preventive blood test - you can sign up for one at uPatient.

Do you need help?

. Make an appointment

See also:

What are blood tests and what do they consist of?
Blood tests are one of the most commonly performed laboratory tests. They make it possible to examineand, among other things, the concentration of chemicals, levels of proteins and cells present in the blood. Through blood tests, it is possible to make an initial determination of the patient's condition, as well as to detect numerous diseases.

Why are blood tests performed?

Blood tests include dozens of tests that can be performed for various reasons. However, they are most commonly performed for several reasonsand.

Checking your general health. Basic blood tests such as a blood count allow you to check your general health.
Diagnosing a disease. If the patient's symptoms or the results of previous tests make it possible to suspect a disease, selected blood tests can confirm or exclude it.
Monitoring treatment. If a patient is taking medication or undertaking other treatment, blood tests can be helpful in monitoring their condition.

When should blood tests be performed?

Basic, preventive blood tests, such as a blood count, lipidogram or liver tests, should be performed once a year. However, if there is something wrong with your body - don't wait and go for tests immediately.

Blood tests are a good idea.

Recommendationsand for basic blood tests:

weakness,
.
fatigue,
.
weakened immune system (recurrent infections),
.
easily appearing bruises,

slower healing,

slower healing.
slower wound healing,
.
decreased mood,

decreased mood.
sleeping problems,

disorders of concentration,

disorders of concentration,

disorders of mood.
disorders of concentration,

disorders of concentration.
pain in muscles, joints, bones,
.

Seniors also need to remember about blood tests. Older people are much more prone to diseases of, for example, the circulatory or skeletal systems, and their immunity is much lower than that of the young. This is why seniors should have regular blood tests. They make it possible to treat diseases at an early stage, which, if untreated, can quickly develop into dangerous conditions.

Please note!

Remember that all unusual symptoms that cause discomfort should be consulted with your doctor. Make an appointment and get your health checked.

Where to get blood tests done?
.
Basic blood tests, such as a blood count, can be done at most GP surgeries. For more advanced tests, on the other hand, you should go to a laboratory with a doctor's referral.

You can also do blood tests privately with the help of services such as uPatient. Once you have selected a specific package of tests, choose your location and a mobile medical specialist will come to take your blood.

Provided you have a blood test, you can choose to have your blood drawn.
.

Do you need help?
. Make an appointment
.

How long is the waiting time for blood tests?
.
The waiting time for blood tests depends on the facility you choose and the set of tests. If you opt for a preventive test package from uPatient, the test - if there are free appointments - can even take place the same day. You will receive the results electronically two days later.

The situation is very similar for blood tests performed on the National Health Service. In most cases, they can be done on the day you receive your referral. However, if the waiting volume is too high, it will be necessary to choose a different date.

The cost of a blood test is also very high.
How much do blood tests cost?
.
Blood tests can be done for free with a referral from your doctor. However, if you want to perform them on your own, you will have to pay. The cost depends on the parameters you want to test. In most cases, it is most beneficial to opt for a package of several tests offered by the laboratory.
.
On the uPacjenta website, you will find various sets of tests, e.g. preventive tests (cost: PLN 200). Several tests are included in this package, such as the determination of the concentration of magnesium, iron or morphology.

.
If a test detects, that you have a magnesium deficiency, it is worth considering supplementation.

In this article you will find the best preparations with this mineral: Best magnesium - ranking

.
.
If your GP consistently refuses to refer you for tests - and you know, that your request is justified - go to another specialist.

.
Witold Tomaszewskidoctor of medical sciences
.
.

.

Do you need help?
. Make an appointment
.

How to prepare for a blood test?
.
For any blood test, it is important to prepare properly. It is best to ask your healthcare professional for precise instructions. What do the most common recommendations includeand?

.
Refrain from eating. For the vast majority of blood tests you should come in fasting. Sometimes you will not be able to eat or drink for only a few hours before the test. In other cases, you will need to abstain from food already the day before the test itself.

Exhibit selected foods. Some blood tests do not require complete abstinence from food, but you may need to avoid specific foods (e.g. meat or herbal tea) before the blood draw.

Do not drink alcohol. Tests, such as liver tests, require us to be abstinent for several days prior to blood collection.
.
Avoid selected activities. Some blood tests require the avoidance of certain behaviours, such as sexual activity or strenuous exercise.

Some blood tests require the avoidance of certain behaviours, such as sexual activity or strenuous exercise.
Do not take medication or supplements. If you are taking any medication or supplements, consult your doctor. You may need to stop taking them a few days before the test.
.
Avoid smoking tobacco products. Some blood tests cannot be carried out if you have smoked cigarettes in the last few hours or so.
.

Before some blood tests you will be asked to drink a bottle of water. This will help to keep more blood in your veins - this can be crucial to getting accurate results. In contrast, for other tests you should drink less fluids. Always ask your healthcare professional how much water you should consume before the test.

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Being fasted before the test means eating a light meal a maximum of 8-12 hours before the test. You can drink water, but only plain, clean water. Do not add sugar or lemon to it.
.
.
Ilona Krzak Master of Pharmacy

.

.
Caution!
.
Not following the instructions of your healthcare professional may affect your test results. If you have not followed the instructions - always be honest and inform the specialist at the laboratory and the doctor interpreting the test results.

How long to wait for a blood test after taking an antibiotic?
.
While taking an antibiotic, you cannot undergo blood tests. On the other hand, you should wait from a few days to even a few weeks after stopping antibiotic therapy. If you have finished taking an antibiotic and are wondering whether you can go for blood tests - contact your doctor.

Only a specialist can give you the green light. Acting on your own can result in unreliable test results.

Can blood tests be performed during your period?
.
Yes, blood tests can be performed during menstruation (period). Although this may affect your test results, if you tell your doctor that you are having your period, the specialist will take this into account when interpreting them.

.

Do you need help?
. Make an appointment
.

What and how can blood test results be affected?
.
On the internet you can find information about how particular factors interfere with test results. However, there is not a lot of reliable data on what and how specific behaviours affect them, so I asked Ilona Krzak, MSc pharmacy.

What factors interfere with test results and what failure to follow the doctor's advice can result in?
.
Stress
.

An increase in fasting glucose
.
Increase in total cholesterol, LDL cholesterol, triglycerides, and decrease in HDL cholesterol.

Increase in insulin.
Increase in insulin.
.
Increased sodium ion levels.

Increased sodium ion levels.
Increase in cortisol and prolactin.
.
Decrease in testosterone.
.
Decrease in immunity - fewer antibodies. This manifests itself in test results with a decrease in lymphocytes, eosinophils and monocytes.

Decrease in immunity.
Decrease in progesterone.
.

Sex
.

Increase in prolactin.
.
Increase in testosterone.

Increase in testosterone.
Rise in PSA - a tumor marker in prostatic (prostate) hyperplasia.

Rise in PSA - a tumor marker in prostatic (prostate) hyperplasia.

Alcohol
.

Increase in hepatic tests ALAT and ASPAT.

Increase in liver tests.
increase in bilirubin, triglycerides, oestradiol, adrenaline, aldosterone, uric acid and cortisol.

Intensive exercise
.
Increases:

Total protein,
.
D-dimers,
.
adrenaline,
.
cortisol,
.
glucagon,
.
ACTH,
.
prolactin,
.

Falls:
.

glucose,
.
cholesterol,
.
triglycerides,
.
blood clotting time,
.
testosterone,
.
insulin,
.

.
Note!
.
Make sure to avoid stress, exercise sexual restraint, abstain from alcohol, and avoid strenuous exercise before the blood test.

.

Are you in need of help?
. Make an appointment
.

What are the contraindications to having blood tests done?
.
The most common contraindication to blood tests is infection. During illness, most of them should not be performed. Other contraindications relate to specific blood tests, so it is important to talk to your doctor. It is the specialist who decides whether selected blood tests can be performed.

Basic blood tests and result standards
.
Blood tests include dozens of different parameters. However, there are a few basic ones that are worth testing at least once a year.

Blood morphology
.
Blood morphology is one of the most basic blood tests to assess the patient's overall health. With it, it is possible to detect infections or leukaemia, for example. What does a complete blood count test look like and what are the reference values (norms)and?

red blood cells - men: 4.35-5.65 million/mcl, women: 3.92-5.13 million/mcl.

.
white blood cells - adults: 3400-9600/mcl.
.
hemoglobin - men: 13.2-16.6 g/dl, women: 11.6-15 g/dl.
.
haemoglobin - men: 38.3-48.6%, women: 35.5-44.9%.
.
platelets - men: 135,000-317,000/mcl, women 157,000-371,000.

Blood morphology tested privately costs around £10-15.
.
.
Note!
.
Remember that reference values (norms) can vary from laboratory to laboratory, so it is up to your doctor to interpret your test results.

Lipidogram
.
Lipidogram includes total cholesterol, LDL ('bad' cholesterol), HDL ('good' cholesterol) and triglyceridesand. This blood test can detect health problems such as coronary stenosis, assess the risk of myocardial infarction or stroke. What are the reference values for each parameterand?

Total cholesterol: less than 200.

Total cholesterol: less than 200.
HDL cholesterol: 60 or more.

Total cholesterol: less than 200.
LDL cholesterol: less than 100.
.
Triglyceridesand: less than 150 mg/dl.
.

The price of a lipidogram test is around £20-40
.
Glycaemia
.
Glycaemia determines the concentration of glucose (blood sugar). Most commonly this test is used to diagnose conditions such as type 2 diabetesand. You must attend for it on an empty stomach (we must be without a meal for at least 12 hours). What might the results indicate?

99 or less mg/dl: sugar concentration correct.

100 or less mg/dl: sugar concentration correct.
100-125 mg/dl: possible pre-diabetic state.

100 to 125 mg/dl: possible pre-diabetic state.
126 or more mg/dl: possible diabetes.
.

A blood glucose test costs around £20-30
.
How to prepare for a blood glucose test?
.
.
Be fasting. Any meal eaten immediately before the test may affect the result.

Be fasted.
Be well rested, after sleeping through the night. Stress, nerves, or a sleepless night can interfere with your blood glucose result.

Be rested, after a good night's sleep.
Avoid exertion. Go to the test with a leisurely walk, without much effort.

Do not drink.
Do not drink alcohol. You may not consume alcoholic beverages for a few days before the test.
.

In addition to these recommendations, you should also take into account the medications you are taking. They too can interfere with the result.

.

Do you need help?
. Make an appointment
.

.
The blood glucose meter is not designed to diagnose diabetes. It is merely an instrument with which we can monitor blood glucose indications. Glucometer readings and laboratory results can differ by up to 10-15%.
.
.
Ilona Krzak Master of Pharmacy

.

.
Did you know?
.
In addition to basic blood glucose testing, there is also a distinction between so-called adherent testing and OGTT. In the case of the former, testing is performed at home - either before or after a meal (the patient does not need to be fasting). The oral glucose load test (OGTT), on the other hand, requires abstinence from stimulants and exercise three days before the test. Once it has started, the patient's blood will be drawn, then he or she will need to drink a glucose solution so that the blood will be drawn again after a specified time.

TSH concentration test
.
The TSH concentration test can detect abnormalities in the thyroidand. Too high a TSH concentration will indicate hypothyroidism of this organ. Conversely, too low a concentration may indicate hyperthyroidism. The reference value for a TSH concentration test is usually :

from 0.4 to 4.0 mIU/l. The price, on the other hand, is around £25-45.
.

CRP test
.
The CRP test measures the concentration of C-reactive proteinand. It can detect, among other things:
.

viral and bacterial infections,
.
intestinal disorders,
.
autoimmune diseases,
.
pulmonary diseases,
.

Most often, low CRP levels do not herald serious health problems. It is the elevation of this parameter that can indicate dangerous inflammatory conditions. The reference value for this test isand:

less than 10 mg/l.
.

Remember that normal results can vary, so it is up to your doctor to interpret your result.

The price of a CRP test is around £15-45.
.
OB test
.
OB (passer's reaction) is a blood test to detect inflammation in the body. It can be helpful in diagnosing conditions such as giant cell arteritis or rheumatism. The reference value isand:

0-15 mm/h for men,
.
0-20 mm/h for women,
.

Obc tests cost about £10-15.
.
Liver tests
.
Hepatic tests (liver function tests hepatic function tests) are a blood test to show abnormalities in the function of this organ. What parameters do they include and what are the reference valuesand?

ALT: 4-36 IU/l
.
AST: 5-30 IU/l
.
ALP: 30-120 IU/l
.
GGTP: 6-50 IU/l
.
Bilirubin: 2-17 µmol/l
.

Abnormal liver test results should be consulted with a specialist. The most common treatments for this organ include a suitable diet, giving up alcohol, and taking a selection of hepatic tablets. However, it is up to your doctor to decide what steps to take. If you are concerned about your health - make an appointment.

Hepatic tests cost 20-50 zloty.
.
.
The results of liver tests can be affected by taking a number of medications such as paracetamol, other NSAIDs (non-steroidal anti-inflammatory drugs), some antibiotics, isotretinoin, immunosuppressants, sulfonamides, ketoconazole.
.
.
Ilona Krzak Master of Pharmacy

.

.
One of the disorders of the liver is liver steatosis.
.
You can learn more about it in this article: Fatty (oily) liver - what it is, causes, symptoms.

.
Coagulogram
.
Coagulogram is a test to assess the blood's ability to clotand. Clotting too easily can lead to a heart attack or stroke. Impaired coagulation, on the other hand, can result in a so-called haemorrhagic diathesis. The reference value for coagulogram results is :

0.8-1.1 INR.
.

The price of the test is approximately £30-300 (depending on the assays chosen).

How long are blood tests valid for?
.
The validity period of a blood test depends on the specific parameters. The most common is several months. A complete morphology is valid for 2 months. After this time - if necessary - you should undergo another test.

How to interpret blood test results?
.
Along with the test results, we receive reference values for each parameter. If our result is within the given range, the test has come out correctly. If not, we may have cause for concern. Remember that test results are influenced by many factors, so it is up to the doctor to interpret them.

.

Do you need help?
. Make an appointment
.

See also:

Sedation tablets [ranking + expert advice]
.
Prescription-free sedation tablets [ranking + expert advice]
.

Summary
.
.
Remember:
.

Blood tests are laboratory tests that allow us to examine the chemicals, proteins and cells present in the blood.

Blood tests are the most common indications for blood tests.
Some indications for blood tests are fatigue, bone pain, and a weakened immune system.

Some indications for blood tests are fatigue, bone pain, and a weakened immune system.
Basic blood tests can be done in the clinic, while for more advanced tests you should go to a laboratory.
.
For most blood tests, you should prepare properly.
.
Basic blood tests include a blood count, lipidogram, blood glucose, TSH levels, ESR, CRP, liver tests and coagulogram.
.
Blood tests are valid for several months.
.

.
FAQ
.
.
How to collect faeces for latent blood testing
.
Collecting stool for a latent blood test may seem complicated. However, in reality it is a few simple steps:

Before passing faeces, empty your urinary bladder.

Before passing faeces, empty your urinary bladder.
Drain into a pre-prepared vessel.

Follow the steps below.
Using an applicator, take samples from 2-3 sites.

Take a sample from the bladder.
Mix the collected samples with the liquid in the tube.
.

Remember to take care when opening the test tube and placing the stool to ensure that no liquid escapes.

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What are the blood tests for the liver?
.
The most basic, preventive blood test for the liver is the so-called liver test. It includes the testing of five parameters: ALAT, ASPAT, GGTP, ALP and bilirubin. With liver tests, it is possible to determine liver function and confirm or rule out various conditions, such as a fatty liver.

If there is something wrong with your liver, it is worth considering tablets or liver supplements.

.
Can HPV be detected from a blood test?
Yes, a diagnosis of HPV (human papilloma virus) infection can be made from a blood test. Moreover, it is even possible to determine - if a person is infected - which type of virus has infected them.

Cervical cancer, the main cause of which is HPV infection, is a very serious condition. However, if detected early enough, it can be curable in up to 99% of cases. Prevention and frequent blood tests are therefore very important.
.
.
Can a GP refuse to refer for blood tests?
Yes, the GP will only make a referral for blood tests if he/she thinks it is necessary. If the specialist feels that the blood tests are unnecessary - they can refuse the referral. However, if you know you are due a referral and the specialist continually refuses it - go to another doctor.

.
What blood tests to do while taking the contraceptive pill?
.
While taking the contraceptive pill, it is a good idea to have the aforementioned basic blood tests regularly: blood count, lipidogram, ESR, CRP, liver tests, coagulogram and TSH levels. It is equally important to examine hormones such as oestradiol, prolactin or progesterone.

cortisol testing and thyroid testing are important preventive measures that, like blood tests, help to avoid many conditions.

.
Can a pregnancy be detected from a blood test?
Yes, blood tests can detect pregnancy 6-8 days after ovulation. One of these is a quantitative blood test. Pregnancy can also be detected by the so-called qualitative hCG determination. This test has a very high efficiency (better than a pregnancy test). Remember, however, that only a gynaecologist can definitively confirm a pregnancy.

.
What tests are due from the National Health Service once a year?
.
The doctor decides whether to refer you for a National Health Fund examination. If the specialist deems it necessary, you can be referred for the same tests several times a year. Otherwise - if the doctor says it is not necessary - you will not be entitled to any National Health Service tests.

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Resources
.
.
See all
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Blood Testing. (2019, December 6). Harvard Health. https://www.health.harvard.edu/diseases-and-conditions/blood-testing-a-to-z

Blood Tests-Blood Tests | NHLBI, NIH. (2022, March 24). https://www.nhlbi.nih.gov/health/blood-tests

Can triglycerides affect my heart health? (n.d.). Mayo Clinic. Retrieved March 15, 2023, from https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/triglycerides/art-20048186

C-Reactive Protein (CRP) Test: MedlinePlus Medical Test. (n.d.). Retrieved March 15, 2023, from https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/

Definition of blood test-NCI Dictionary of Cancer Terms-NCI (nciglobal,ncienterprise). (2011, February 2). [NciAppModulePage]. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/blood-test

Erythrocyte Sedimentation Rate-Health Encyclopedia-University of Rochester Medical Center. (n.d.). Retrieved March 15, 2023, from https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=erythrocyte_sedimentation_rate

How to Prepare for a Lab Test: MedlinePlus Medical Test. (n.d.). Retrieved March 15, 2023, from https://medlineplus.gov/lab-tests/how-to-prepare-for-a-lab-test/

Lala, V., Zubair, M., & Minter, D. A. (2022). Liver Function Tests. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK482489/
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Prothrombin Time (PT) Test: Purpose & Results Evaluation. (n.d.). Cleveland Clinic. Retrieved March 15, 2023, from https://my.clevelandclinic.org/health/diagnostics/17691-prothrombin-time-pt-test

What You Need to Know About Blood Testing: MedlinePlus Medical Test. (n.d.). Retrieved 15 March 2023, from https://medlineplus.gov/lab-tests/what-you-need-to-know-about-blood-testing/

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