An average donor hair density is around 75 FUcm² and can rise to over 100 FUcm² on a very good donor area. The hair density is an important factor in how many grafts you can use; obviously the higher density the more grafts available
The donor area is a safe zone where the hair follicles are genetically programmed to not succumb to hair loss. But it is important as hair loss progresses that a conservative approach is taken to the size of the donor safe zone
Hair loss is progressive and can continue for many years, starting generally from the hair line until it reaches the crown; the hair loss stages are categorised from minimal loss (NW2) to NW7 advanced hair loss.
Dependent on the technique used will determine how the follicular units are removed and how many FU´s can be harvested in one or multiple procedures. It is possible to have more than one hair transplant procedure, either with FUE or FUT; generally the 2nd procedure will not achieve the same amount as the first as the donor density has been reduced with FUE or laxity changed with FUT
The FUE technique extracts the follicular units one by one and over a wider surface area than FUT; the donor should be shaved and the safe zone assessed, checking for miniaturisation especially around the borders of the donor and recipient areas
As the FUE donor surface area has no signified boundary care needs to be taken not to stretch the boundary to try and reach high graft numbers and start to extract in a potential unsafe zone in later years.
FUT harvests the grafts from a single, relatively thin hair bearing strip where the follicles are at the highest density. The strip is then divided to remove the individual follicular units, 1, 2, 3 and 4 hair units
FUT relies much more on skin laxity rather than needing to harvest over a wide surface area; and because of the high concentration of FU´s in the area on an average candidate 4000 grafts can be removed in one procedure.
On a good candidate anything from 6-7000 grafts can be harvested in one day with FUT. FUE generally in one procedure around 3000 can be achieved, partly due to the slow harvesting and to not over harvest.
With good laxity with FUT a 2nd procedure could yield a further 3000 grafts, FUE probably much lower because of the reduction in hair density from 100% prior to any surgery to around 70-75% after the 1st procedure
An average hair transplant candidate with FUT can reach around 7-8000 grafts over multiple procedures, over multiple procedures with FUE this figure will generally be lower, unless harvesting exceeds 50% of the donor hair
Planning is vital from the very first procedure to ensure long term the donor is kept in the best cosmetic condition and the maximum number of grafts can be removed if/when hair loss progresses