Haematopoietic stem cells can be drawn from venous blood or bone marrow.

The harvesting of haematopoietic stem cells from venous blood takes place in an outpatient clinic, meaning that donors can return to their place of work or home after the collection is completed. Five days prior to the collection, a donor is administered one subcutaneous injection of medicine twice a day, which stimulates the multiplication of haematopoietic stem cells in their bone marrow and their transition into blood. Ordinarily, donors feel moderate bone and muscle pain, nausea or a headache, as if they had the flu.

With a special automated procedure called apheresis, haematopoietic stem cells are harvested from the donor's blood, which runs through a needle and a system of tubes into a special apparatus, and are collected in a special bag. The harvesting procedure using the apparatus takes from 4 to 6 hours and is similar to collecting platelets. This method of collection is used to harvest only haematopoietic stem cells from a donor, while the remaining blood components are returned to the donor.

When haematopoietic stem cells are harvested from venous blood, the donor, as already mentioned, may feel pain due to a medication that accelerates the propagation of haematopoietic stem cells. The pain is relieved a day or two after the last dose is administered. The donation of bone marrow or, rather, haematopoietic stem cells by no means implies a major risk to the bone marrow, immune system or any other disease.

In the other hand, so-called classic or surgical harvesting, which is performed under general or local anaesthesia, a special sterile needle and syringe is used to extract 2 to 3% of red bone marrow from various points of the flat pelvic bone. The procedure takes 1 to 2 hours. The bone marrow collected in a special plastic bag looks like blood, but is thicker. The donor's bone marrow is entirely renewed within 4 to 6 weeks. As a rule, a donor is admitted to hospital a day before the collection and leaves the hospital a day after the procedure. Before bone marrow is drawn, all prescribed medical tests, including those required for anaesthesia, are performed. A week or two before drawing, the donor's blood is taken at the Blood Transfusion Centre of Slovenia and is returned to the donor after the procedure is completed as autotransfusion in order to replace the volume of liquid tissue taken from the donor.

The risk involved in the donation of bone marrow is minimal for the donor. Complications due to anaesthesia are extremely rare, but nevertheless possible and, in exceptional cases, haemorrhage or an infection may occur at injection site. Obviously, donors may feel mild pain at injection site for a brief period of time, but not longer than a week or two.