Venesection (phlebotomy)

Taking blood - called venesection or phlebotomy in medical language - reduces red blood cell counts in people with polycythaemia vera (PV).  It has very few risks.

If you have polycythaemia vera (PV) you have too many red blood cells. One way to reduce your red cell count that does not require any medication at all is to use a procedure called venesection or phlebotomy.

It’s a simple procedure done just like having a blood draw or making a blood donation – a doctor or nurse inserts a needle into your vein and collects some blood. Patients with PV usually have about anywhere from 350 ml to 500 ml of blood removed during venesection. The amount depends on your height and weight as well as your haematocrit, (blood thickness or packed cell volume level) and your general state of health.

How it works

Phlebotomy (or venesection) is a standard treatment for PV and helps bring your red cell count closer to normal. Your haematologist will ask you to come to hospital to have some blood removed. It works in the short-term since you make up the liquid part of your blood (plasma) quicker than red cells and in the long-term iron stores are reduced slowing down the production of red cells. For this reason it is very important not to take iron if you are a patient with PV.

You may need regular venesections every few weeks or months until you reach an acceptable blood thickness level. Your target blood thickness (haematocrit) depends on your risk factors, how well you tolerate the procedure and whether you’ve had any previous complications such as a blood clot.

Why try this treatment

Phlebotomy has some real advantages for people with PV:

  • It works quickly
  • It doesn’t require any medications
  • It has minimal side effects
  • It is effective at reducing red cell counts (and thus risks)
With regular venesections, your haematocrit (or packed cell volume)can reach a normal level, allowing your heart to pump blood more efficiently. However phlebotomy does not reduce white cells or platelet levels.

Together with medication

You may need low dose aspirin therapy and/or a cytoreductive treatment such as hydroxycarbamide, interferon or anagrelide in addition to regular phlebotomies. Your haematologist will work with you to find the best combination for your individual condition.

Common side effects

You may feel tired after giving blood, and you may have some local soreness or bruising, but serious side effects are very uncommon. Some people faint after giving blood, if you feel dizzy or unwell in the 24 hours afterwards tell your team and they may give you some fluid (salt water) to replace the volume lost in the blood. This is more likely to happen if you are taking tablets for blood pressure and if you have not eaten before attending the hospital.

Top tips

These are top tips for phlebotomy shared by people with PV. Share your top tips by emailing us at info@mpnvoice.org.uk.

  • Fainting You can prevent fainting by eating something before your venesection.  Don’t skip breakfast!
  • Replenish Drink plenty of water before and after venesection and be careful of dehydrating drinks.
  • Take it easy Plan a restful time after your venesection.  You may feel a bit tired so you don’’t want to schedule too much.
  • Let others know Tell family members and others you trust that you are having a venesection so you may need a little extra help, for instance if you are caring for young children.
  • Arrange transport You may be too tired to drive or travel by public transport right after a venesection, in particular if you are feeling fatigued for other reasons, for instance as a side effect of your MPN.
  • For women It is best (although not essential) to schedule venesections for a time of the month when you are not menstruating.  This will prevent you from feeling excessively tired after venesection.

Venesection FAQs

Can I eat and drink normally? Yes. We recommend that you eat a normal, healthy diet and drink plenty of water.

Can I drink alcohol? It is safe to drink alcohol in moderation, but we recommend you do not exceed the recommended weekly limits of 21 units of alcohol per week for a man and 14 units for a woman. Please ask your nurse or doctor if you require more information regarding alcohol consumption.

What if I want to have a child? Venesection or removal of blood is a safe treatment if you are pregnant or planning to father a child. If you are pregnant, you may need fewer phlebotomies during your pregnancy. Please see our pregnancy section for more information on pregnancy in MPNs.

Who will do my venesection? Your doctor or a specially trained nurse will take blood.

Can I drive? You may feel faint or fatigued after venesection. If you are feeling drowsy or fatigued for any reason do not drive.

Do I need to take any special precautions? Please make the nurse performing your venesections aware if you have any of the following conditions or are taking any of these medications:

  • If you are taking warfarin.
  • If you are taking beta-blockers (drugs which control blood pressure).
  • If you weigh less than 7 1/2 stone (49kg).
  • If you have previously fainted or felt unwell after a blood test or venesection.
  • If you are frightened of needles.
  • If you have a serious heart condition.

If any of the above applies to you, your medical team may need to take special precautions to ensure that venesection can be carried out safely.