Phlebotomy (Blood Tests)

A Guide to Having a Blood Test

Patient Information

There are a number of reasons why your Doctor may request that you have a blood sample taken. This might be to help with a diagnosis, to monitor treatment, or to exclude certain conditions. In most cases these samples will be taken by a procedure known as Phlebotomy or Venepuncture, i.e. taking blood from a vein. The information given below will explain the procedure in more detail.

How is a Blood Sample Taken?

The procedure is performed by a trained member of staff, usually a phlebotomist, health care assistant, nurse practitioner, doctor or nurse. A tourniquet is placed around your arm just above the elbow, the area is cleaned and then a small needle is inserted into a vein on the inner arm. Blood is withdrawn into sample bottles and the needle is then removed. Pressure is applied at the site with a piece of cotton wool or gauze until the bleeding has stopped and then a small plaster is applied. Please tell the person taking the blood if you are allergic to sticking plaster.

Will it Hurt?

Putting the needle into the arm involves a pin prick sensation but after that the rest of the procedure should be quite painless. Some people continue to feel some discomfort or pain and we are not sure why. It is probably because of nerves under the surface of the skin but this should settle quite quickly. If not you should go to see your GP or a member of hospital staff.

Will it Bruise?

You may get a bruise or a small lump after having blood taken. This will usually settle by itself and fade away in time.
Some conditions may increase the risk of bruising. These include:

  • Drugs such as Warfarin or Aspirin
  • Conditions such as a bleeding disorder or low platelets (thrombocytopenia)
  • When it is hard to get a vein, for example if the arm is swollen (oedema)
  • Elderly patients

To help reduce this risk as much as possible, please tell the person taking the blood if you have any such conditions or if you have had a problem in the past after a blood test. Pressing firmly on the site until the bleeding has stopped should help to reduce any bruising.

Please remember to drink plenty of fluids the night before and the morning of your appointment, this will make it easier for the person taking your blood.

If possible keep the arm slightly raised and avoid too much movement of the arm, such as lifting or carrying heavy parcels, for an hour or so after the blood test.

Should you experience excessive bruising or prolonged bleeding, then apply further firm pressure to the area. A few ice cubes wrapped in a towel may help reduce any swelling and bruising. Bruising can look very dramatic and some people may find this worrying especially if it appears away from the site where the blood has been taken or is visible for a few days following the procedure. However, it is usually harmless and will go away in time.

What Happens to the Blood Sample?

The samples are tested in the pathology laboratory and the results sent to the person who asked for the sample to be taken. Some samples may need to be sent away for further tests or stored in case we need to refer to them in the future.

Data Protection

By law we are expected, to protect any information we have about you. All of your test results are stored and treated confidentially. No-one except the teams looking after you can look at, or have access to, your test results without your permission.

If you have any questions about this procedure please ask the member of staff taking the sample or the person responsible for your care.

Any personal information is kept confidential. There may be occasions where your information needs to shared with other care professionals to ensure you receive the best care possible.