Stem cells are amazing cells that we all have normally in our bone marrow and blood but only in tiny numbers. They are able to grow into all the different types of blood cell that we need.

To carry out a transplant doctors need to be able to collect large numbers of stem cells. There are two main ways of doing this: a bone marrow harvest or a peripheral bood stem cell harvest.

A bone marrow harvest involves the donor having a general anaesthetic. Whilst they are asleep, multiple small punctures are made into their back of the pelvis bone with a hollow metal needle. The liquid bone marrow is sucked out, cleaned and then frozen.

A peripheral blood stem cell harvest involves collecting stem cells from the blood. Normally there are just a few stem cells in the blood, not enough to use for a transplant. To increase the numbers of stem cells in the blood, special growth factors are given as daily injections under the skin. These cause lots of stem cells to flood out of the marrow and into the blood. These can then be collected using a special machine, which filters the blood, collected through a needle in a vein, skims off the special cells and returns the rest of the blood through another needle in another vein.

A bone marrow harvest involves an overnight stay, a general anaesthetic and you can feel quite bruised afterwards, sometimes needing simple painkillers for a day or so.

A stem cell harvest is easier and is usually done as an outpatient. But it does need two good veins and you will need to lie fairly still for around 4 hours. Sometimes the collection needs to be repeated. Also the growth factors needed before the harvest, can have some side effects, such as bone pain or headache.

A stem cell transplant is a very special procedure and doctors will spend a lot of time discussing with a donor the best way for this to be done in each individual situation.