How long it takes to see results from your red light hair treatment depends greatly on the cause of your hair loss and the general condition of your hair and scalp. Less advanced hair loss with limited damage to the follicles should respond better to the red light, so you may see an improvement in hair density and thickness sooner than with late-stage alopecia.
On average, it is not uncommon for a full treatment to take 3-6 months (or over 20-30 sessions), so remember that this is a marathon, not a sprint, and don't be discouraged if you don't see new hair growth after the first few sessions.