Like so many things in life, LLLT is gradual, not instant. Hair grows in cycles, so visible change takes time and regular sessions. Stopping early makes it difficult to judge whether the device is helping. Follow your treatment schedule and judge progress monthly with photos, taken in similar lighting and angles, rather than scrutinizing your hair every day.
There's an increasingly popular option for people dealing with hair loss. It's low-level laser therapy (LLLT) and uses gentle light through a diode-coated hat you put on your head. Before buying a new device, however, you must understand its intended use and how to apply it properly.