It can take many weeks for the chemotherapy drugs to work their way out of your system.
Some people may see regrowth before the end of their chemotherapy treatment, but this is usually only with taxane drugs. For others it can take many weeks, while most patients will see regrowth by 12 weeks after their chemotherapy treatment is completed.
The normal hair growth rate usually returns within several weeks to several months after the last chemotherapy infusion. After hair has grown back, the resting phase of the hair follicle cell cycle lasts for 2-6 months, even after repeated episodes of chemotherapy-induced alopecia. This shows that the hair cycles have not been materially altered.