Blood samples

Blood is the most common specimen used in laboratory testing, as blood tests provide extensive information about the functioning of the body.

Blood samples are used in diagnosing various diseases, monitoring treatment, and screening. Typical conditions investigated through blood tests include infections, blood cell counts, blood disorders, and the functioning of the liver, kidneys, endocrine organs (such as the pituitary gland, thyroid, pancreas), and heart.

During blood testing, an electrocardiogram (ECG) or a urine sample may also be taken if requested. In connection with a glucose tolerance test, additional blood tests may be performed. In such cases, the appointment is booked through the Glucose tolerance test service. Other blood samples are taken before the glucose tolerance test begins.

The specimen types used in blood sample testing may vary by region. If plasma is used as the specimen, the test prefix is P or fP. If serum is used, the prefix is S or fS. The difference relates to the laboratory method used and whether the test requires fasting (fP or fS). Reference values may also vary due to technical differences in testing methods.

Important

Proper preparation according to instructions is a crucial part of obtaining reliable laboratory results. Please inform the sample collector if you have not followed the instructions.

How do I prepare for blood sampling?

Many factors before sample collection can affect laboratory examination results. Therefore, it is important to prepare for sampling according to the instructions provided by your physician or nurse. Please inform the sample collector if you have not followed the instructions.

Fasting or sampling at a specific time

Most laboratory examinations do not require fasting or a specific time, and samples can be taken during laboratory opening hours.

Check your patient instructions to see how to prepare for the examination. For a fasting sample, you must refrain from eating for 10–12 hours. During fasting, you may drink a glass of water.

Some laboratory examinations require sampling at a specific time. In these cases, your physician or nurse will instruct you to come to the laboratory at the designated time.

General factors affecting laboratory tests

Many factors such as eating, physical exertion, stress, coffee, tobacco, alcohol, and medications (including herbal products and vitamins) can affect laboratory examination results. On the morning of sampling, avoid smoking, caffeinated beverages, and intense physical activity. Avoid alcohol during the 24 hours before blood sampling.

Before blood sampling, it is recommended to sit calmly for about 15 minutes to stabilize circulation.

Laboratory examinations and medications

Medications can usually be taken as normal unless otherwise agreed with your treating physician. If it is necessary to measure the concentration of a medication in the blood, the morning dose should be taken only after the blood sample has been collected.

What happens during blood sampling?

Blood is usually drawn from a vein in the elbow crease. Multiple sample tubes may be collected at once, depending on the requested examinations.

Sometimes blood may be drawn from a fingertip or, in infants, from the heel. In hospitals, a nurse or physician may also collect a blood sample from a cannula inserted into a vein.

What should I be aware of after blood sampling?

After venous sampling, it is recommended to sit calmly and apply continuous pressure to the puncture site for about five minutes to stop bleeding.

Giving a blood sample does not require follow-up and does not restrict normal daily activities. Your attending physician will inform you of the results and how treatment will proceed. Contact your care unit if you do not have a scheduled appointment or call time.

Are there any risks associated with blood sampling?

Blood sampling is a safe procedure. The most common side effect is bruising at the puncture site due to blood leaking under the skin.