Blood tests

Blood tests form an important part of diagnosing cancer and monitoring how patients are responding to treatment. By examining samples of your blood, healthcare professionals can learn about your general health as well.

Taking a blood sample

The most common way a sample of blood will be taken is from a vein in your arm. The veins are relatively close to the surface of your skin at the inside of the elbow or wrist. Sometimes it might be necessary to take the sample from the back of your hand. If you need to prepare in a specific way for your blood test, for example not eating beforehand, you will be told in advance.

In order to slow the speed at which blood is moving through your veins, the nurse or doctor may tighten a strap or band around your upper arm. This causes the veins to swell temporarily and makes it easier for the nurse or doctor to find a place to take the sample.

Generally, a blood sample is taken using a needle attached to a syringe. While not painful, some patients experience a slight pricking feeling when the needle is inserted. If needles and injections make you feel anxious, tell the person who is taking the sample, so that they can make you more comfortable.

After having a blood sample taken

If you feel dizzy or faint during or after a blood test you may find it helps to lie down. Tell the doctor or nurse who is taking the sample. Usually only a small amount of blood is taken so you should not feel ill from loss of blood.

As a result of the test, you may have a small bruise in the skin around the needle prick. The most common causes of bruising after a blood test are lack of pressure on the site of the jab until the bleeding has stopped, or if the needle damaged the vein or other blood vessels while it was being inserted. Although bruises can be painful, they are usually harmless.

Once your blood sample has been examined, the results will be sent to your consultant and discussed with you at your next appointment.


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www.royalmarsden.nhs.uk/cancer-information/detection-diagnosis/blood-tests

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