Can gray hair caused by insufficient qi and blood turn black again?
Generally speaking, whether gray hair caused by insufficient qi and blood can turn black again depends on the specific circumstances. If you experience any discomfort, it is recommended to seek medical advice promptly. The detailed analysis is as follows:

If gray hair has appeared recently and only in small amounts, and the hair follicles have not completely atrophied, some gray hairs may regain their color through timely regulation of qi and blood. This situation commonly occurs due to recent fatigue or dieting-induced deficiency of qi and blood. By improving nutrition, maintaining regular sleep patterns, and consuming blood-nourishing foods, hair follicles can receive adequate nourishment. As a result, melanin production function gradually recovers, and newly grown hair will appear black.
However, if gray hair has been present for a long time, is widespread, or is accompanied by hair follicle atrophy and scalp aging, simply regulating qi and blood is unlikely to restore the original color of already-grayed hair. This condition often results from prolonged qi and blood deficiency leading to deterioration of hair follicle function and loss of melanocyte activity. Even with improved qi and blood circulation, damaged hair follicles cannot be reversed, and newly grown hair may remain gray.
In daily life, it's advisable to consume more blood-nourishing foods such as red dates, black sesame seeds, and longan. Ensure sufficient sleep and avoid staying up late or excessive fatigue. Be gentle when combing your hair to minimize scalp irritation, and maintain a cheerful mood to prevent anxiety from further depleting qi and blood.