Blood test

Potential causes of many physical symptoms and diseases can be identified in the blood, and blood tests can also show how well a medication is working. To find this out, blood testing is needed. For that, blood must first be drawn.

Where can you have blood drawn?

Your GP or a medical specialist requests the blood test. The person drawing the blood then knows how much blood is needed and how many tubes are required. The laboratory technician who later examines the blood also knows what to look for. The doctor who orders the blood test will indicate whether you need to fast and whether you should temporarily stop taking any medications. If fasting is required, you may not eat or drink during the 8 hours before the test.

Blood is taken at designated phlebotomy centers. These are often located at GP practices or hospitals. But there are also many other locations in the community. Many centers also offer early morning or evening hours. Useful if you need to fast or prefer to go after work. Sometimes it is necessary to make an appointment. This can often be done online. Ask for a location nearby.

How does blood collection work?

The staff member of the blood draw checks whether the person on the request is the same as the person who comes for the blood draw. The staff member prepares the appropriate tubes and labels them with a sticker containing the patient's details. People who are afraid of needles should indicate this right away. The staff member will then take this into account. You must always be seated.

Then a tight band is placed around the upper arm. This tourniquet causes the vein to swell slightly, possibly in combination with a clenched fist, and become easier to see. This makes it easier to draw blood.

After the puncture site is disinfected with a bit of alcohol, a hollow needle is inserted into a vein. This is usually in a vein in the elbow crease. This may be briefly painful, but that is short-lived. The tube then slowly fills with blood. If multiple tubes of blood are needed, they are changed during the draw.

These tubes contain an anticoagulant that keeps the blood fluid. This is important to be able to test the blood. When enough blood has been collected, the staff member removes the needle from the vein.

By pressing a cotton swab on the puncture site, the bleeding stops, after which a bandage is applied. The blood draw is now over. Sometimes a bruise develops afterward. This usually disappears within a few days and is harmless.

By gently shaking the tubes, the blood mixes with the anticoagulant. This is done by hand or with a special device. The blood is then sent to the laboratory for analysis.

What can be seen in a blood test?

Blood contains, among other things, blood cells, nutrients, building materials and waste products. The composition of the blood provides important information about health, how well the organs function and whether a treatment is working.
Examples of what can be measured in a blood test include:

• Inflammation markers (these indicate inflammation somewhere in the body).
• Iron level.
• Blood sugar level.
• Proteins.
• Waste products.
• Medication levels.
• Hormone levels.
• Antibodies against a specific disease.
• Bacteria and viruses.
• Toxins such as alcohol and drugs.

The result

The results of the blood test are usually available within a few days and can be obtained from the (family) doctor or viewed online. The doctor discusses the results with the patient. To determine whether something is abnormal, the doctor compares the measured values with the reference ranges.

Reference ranges are measured in a large number of healthy individuals. An average range is then calculated. If your value is above or below that, it is considered outside the normal range. For example, a normal value might be somewhere between 5 and 10. If your result is above or below that, it is considered abnormal.

The doctor combines the blood test results with any other tests and the reported symptoms. Based on this, the doctor decides on the next steps. There may be a referral to a (different) medical specialist, a change in medication or no change at all. This is always done in consultation with the patient.