Does hair extracted for hair transplantation grow back?

Does hair removal for transplantation grow back? NO!  That is why you need to make sure you will have enough hair to complete a transplantation before you start.      

Extracted/ harvested hairs do NOT grow back. You WILL have a scar (with no hair) no matter which technique is used.  FUE scars will leave thousands of white dots and FUT scars will leave a linear line.  This is not meant to sound fatalistic, but that is the reality of ANY surgical procedure.  There are many techniques used by surgeons to minimize the appearance of a scar but there will still be a scar.  Fortunately most scars are small enough for hairs to cover them.

All hair transplants whether FUE or strip (FUT) lead to loss of follicles from the area they are taken from.  That's why decisions on hair transplants are so important - the hair doesn't grow back once taken out. The hair loss is often less noticeable with FUE (heals as small dots) than FUT (heals with a line-type scar).

I practice the Neograft FUE hair restoration procedure,
where I move the hair from a healthy donor site, (usually the back of the
head/neck), and transplant the healthy hair follicle onto the balding area.
Once the follicle is removed from the donor area, it will not regrow, but the
percentage taken is usually minimal and not noticeable. There is little to no
scarring, as the device we use to extract
the follicle is less than 1 mm diameter. The tiny hole doesn’t need suturing.
The grafts are placed into a needle stick and are held in place without
sutures. The delicate grafts are handled by the machine and inserted
pneumatically so that they are less likely to be injured (which means a higher
amount of ‘take’ or success). Typically, people don’t develop scarring from
needle sticks so no one can even tell you had it done. Some patients even
return to work the next day.

It is true that if an entire FUE is extracted from the donor area then no hair will grow back in the donor area.  I find that using a technique I call microFUE whereby only a portion of the follicle is extracted using a sub-millimeter punch size some follicles will regrow in the donor area because enough follicular components remain.  It is not fully understood how this happens, however with the addition of PRP and growth factors, some regeneration is clearly recognized.