What is a therapeutic venesection?
Therapeutic venesection is a procedure that removes a small amount of blood, to treat conditions involving excess iron, red bloods cells or specific blood disorders. Therapeutic venesection is a safe procedure, without side effects in most cases. It is a similar process to a standard blood donation.
How to prepare for your venesection
- Your treating team will advise you if you need to do a blood test before your venesection. This is generally required to be done within 4 weeks of the procedure.
The day before your venesection
- Drink plenty of water (1-2 litres), your blood volume goes down a little after the procedure.
In the 3 hours before your venesection
- Drink 750ml (3 glasses) of water
- Eat something savoury
- Avoid strenuous exercise
What to expect
- Before the venesection is carried out your nurse will explain the procedure to you and ask you a few questions regarding your medical history. They will check your blood pressure and heart rate.
- A cannula is inserted into a vein in your arm. The cannula is secured into position with tape. A bag is connected to the cannula for the purpose of collecting the blood.
- This is not a painful process. The pain that may be felt during this procedure is when the needle initially punctures the skin, but that does subside.
- It takes about 15 minutes to drain approximately 450 ml of blood.
After your venesection
- Following your procedure the cannula will be removed, and the site will be covered with a dressing. Keep this on for 2-3 hours.
- Your blood pressure and heart rate will be checked again.
- Immediately after the procedure you may feel dizzy. This can be minimised by resting, not standing from sitting too quickly, having a snack and drinking fluids.
For the rest of the day
- Drink plenty of fluids, aim for 3 glasses in the first 3 hours.
- Eat regular meals
- Take time to rest and recover, you may feel a little tired for a couple of days.
- Avoid alcohol for the next 24 hours
- Avoid strenuous exercise for at least 12 hours and try not to overheat.
If you experience any of the following, please contact your treating team, GP or attend the Emergency Department
- Bleeding at the puncture site (apply pressure and cover until it stops)
- Redness, discharge or a lump at the puncture site
- Fever
- You feel unwell
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Consumers were consulted in the development of this patient information.
Last consumer engagement date: 4/8/2026