FUE donor supply, what you must know if you are going to have an FUE hair transplant. – WRassman,M.D. BaldingBlog
Look at your donor supply as a bank account, but it has follicular units (grafts) instead of money. Caucasians are born with 110,000 hairs or 50,000 follicular units (grafts) of which something between 10,000-12,500 that contain permanent hairs. It is a simple calculation that if there are 50,000 grafts (follicular units which I am now interchanging in terminology) so by dividing 110,000 hairs by 50,000 grafts, you get roughly 2.2 hairs/graft which is the average number of hairs/graft in the entire head. Only the permanent grafts are the 10,000-12,500 grafts around the back and side of the head, a 3 inch high zone that we can harvest and move these grafts to other parts of the scalp where hair is either missing or thinning. As these grafts contain a different genetic code, they are programmed in most men, to last the lifetime of the man. If you are Asian or African, your total number of birth hairs are less than Caucasians but the total number of grafts remain the same.
So if we harvest (remove) grafts from the permanent zone (the donor area), then this bank of hair gets reduced by the number of grafts that are removed. For a person with medium weight hair, the surgeon may be able to remove up to 60% of these grafts without significantly impacting the hair coverage of the donor area. In fine haired men, the number of grafts that can be removed will be significantly less than 60^ of the total donor supply, while in coarse haired men, the total number of grafts that can be removed, will be greater than 60%. Everyone who has grafts removed from Follicular Unit Excision (FUE) run a real risk of donor site depletion that is proportional to the number of grafts removed. If a surgeon removes 8,000 grafts in a person with medium weight hair, the donor area could be depleted enough that it becomes very thin, patchy and even see-through. Each patient needs to have a discussion with their surgeon about where they stand with regard to complications of over-harvesting the donor area. Every patient should expect to have no surprises, so developing balding in the donor area from FUE is a risk that every patient takes when they undergo an FUE hair transplant surgery.