Normal hair density – in individuals not suffering from hair loss – is somewhere between 80-100 follicular units per square centimetre of the scalp. Thinning is not visually obvious until approximately 50% of the native density has shed. This means transplanting between 45-55 follicular units per square centimetre during hair restoration procedures is normally sufficient. Implanting at densities of 80-100 follicular unit per square centimetre (“normal” hair density) is usually never done. This happens for several reasons: 1. because it is not necessary and wastes finite grafts; 2. because implanting at this density may overwhelm the blood supply and cause shock loss in the surrounding native hairs; 3. because severe damage or diversion of the scalp blood supply can potentially cause necrosis or other serious issues.
