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Preparing for laboratory tests
Preparing for a laboratory test is important for reliable results. Some tests require fasting or sample collection at a specific time of day. Always follow the instructions you have been given to make sure that the samples are comparable.
General information about preparing for laboratory tests
In most cases, there is no need to prepare for a laboratory test. Most samples can be collected regardless of when the patient has last eaten or the time of day.
See which laboratory tests require:
- fasting or
- a sample collection at a specific time of day.
All recommendations regarding the timing of a sample collection or fasting should be followed to ensure that the sample is as reliable as possible and that the result is easily comparable with the reference values. Learn more about our laboratory services.
Test with or without an appointment?
Normally, you can come to the laboratory for tests without making an appointment. Such tests include tests performed on blood, urine and stool samples as well as ECG.
If you wish, you can also book an appointment for a laboratory test by calling 010 414 00 (local network rate/mobile charge), or by using the OmaMehiläinen service or the online appointment booking service. You can find information about our locations and the opening hours of our laboratories through our location search.
Through our online appointment booking service, you can book an appointment for
- blood and urine sample collection
- a Pap test (cervical screening)
- an ECG test
Sample collection with or without a referral?
You can come to the laboratory with or without a referral.
Please note that you must always have a referral when using our services as an occupational health customer. If you come to the laboratory for a test without a referral from a doctor, the expenses will not be eligible for Kela reimbursement or, usually, for coverage by medical expenses insurance.
How to prepare for a sample collection
The majority of laboratory tests are performed on blood, as it carries various substances, such as cholesterol, sugars, vitamins and hormones as well as antibodies. In addition, blood cells and clotting factors can be tested. The concentrations measured in the blood are used for diagnosing illnesses (abnormally high or low concentration) and monitoring (change in concentration).
Most samples can be collected regardless of when the patient has last eaten or the time of day. Before testing, we recommend that you sit still for about 15 minutes to allow your blood circulation to stabilise.
Eating and drinking before blood sample collection
Unless otherwise agreed with your doctor, you can eat a light meal and drink a little as well as take any medicines you may need before the sample collection. You don't have to fast before the test as, according to the latest studies, samples taken without fasting provide the most accurate information about the risk of illness. This means that you should not fast unless specifically told to do so.
In exceptional cases, a fasting sample is required (in these cases, the abbreviation of the test name will start with a lower-case f, e.g. fP-Gluk). Fasting samples are usually collected in the morning after an overnight fast. You should not eat or drink for 8–12 hours before the sample collection. You can drink a glass of water and take your necessary medication in the morning before the sample collection. You can eat normally on the day before the sample collection. However, you should avoid drinking alcohol.
Some blood samples must be collected in the morning before medication is taken, e.g. if the concentrations of medications are being tested. Your doctor will instruct you if the sample needs to be collected before medication is taken.
Scheduled sample collection
The levels of hormones (e.g. TSH, testosterone) vary depending on the time of day, but samples for thyroid tests, for example, can still be collected at any time of day. However, the testosterone level must be tested from a morning sample.
Usually, samples collected from the throat are used to test for streptococcal infection. Throat swabs can also be used to test for adenoviruses, which are common in children, or a more detailed culture can be done to find a rarer pathogen. The throat swab is taken by rubbing a cotton swab along the tonsils and the inflamed area of the posterior pharynx.
The result of a rapid test will be available within an hour, whereas a throat swab culture will usually take 2–3 days.
One hour before the sample is taken, it is advisable to avoid eating, drinking and using disinfecting lozenges and rinses, as these can reduce the number of bacteria in the mouth and cause a false negative result.
Samples taken from the nasopharynx (nostril) are tested for influenza, coronavirus, RSV and pneumococcal viruses. A nasopharyngeal swab is taken with a thin and flexible cotton swab. The swab is rotated slightly to obtain a reliable sample. The result of a rapid test will be available within one hour and results for other tests usually within the same day.
Various substances leave the body along with urine, the concentrations of which can be measured more accurately. Urine can be chemically screened for sugar, protein, blood, etc. When an infection is suspected, a urine culture is performed to detect bacteria. In some cases, it is necessary to examine urine cells and particles with a microscope. Instead of a single sample, urine collection (24 h) is sometimes required to determine a specific substance concentration.
Preparing for a urine sample collection depends on the test, and the test orderer or laboratory will provide instructions. For urine samples collected at home, you can get a sample container and instructions from the laboratory. Usually, the urine sample is collected in the morning when at least 4–6 hours have passed since the previous urination. Avoid drinking water before giving the sample to avoid excessive dilution of the urine. Do not drink more than one glass of water in the morning. For a urine sample for a pregnancy test, your period should be at least one week late.
The stool sample is tested for pathogenic bacteria and parasites to determine the cause of diarrhoea, for example. The sample is collected at home and brought to the laboratory the same or the next day. The sample container and instructions can be obtained from the laboratory.
