This article reviews the biphasic dose response in low-level laser therapy (LLLT), where low levels of light have better effects on stimulating and repairing tissues compared to higher levels. The authors discuss the historical background, evidence for the effectiveness of LLLT, and the underlying mechanisms at the cellular and molecular levels. They highlight the importance of irradiance and time as key parameters in determining the dose of LLLT. The review also covers the biphasic dose response observed in various studies, including animal models and clinical trials, and proposes possible explanations for this phenomenon, such as excessive reactive oxygen species (ROS) production, nitric oxide (NO) release, and activation of cytotoxic pathways. The authors conclude that further research is needed to fully understand the mechanisms of LLLT and to optimize its use in mainstream medicine.This article reviews the biphasic dose response in low-level laser therapy (LLLT), where low levels of light have better effects on stimulating and repairing tissues compared to higher levels. The authors discuss the historical background, evidence for the effectiveness of LLLT, and the underlying mechanisms at the cellular and molecular levels. They highlight the importance of irradiance and time as key parameters in determining the dose of LLLT. The review also covers the biphasic dose response observed in various studies, including animal models and clinical trials, and proposes possible explanations for this phenomenon, such as excessive reactive oxygen species (ROS) production, nitric oxide (NO) release, and activation of cytotoxic pathways. The authors conclude that further research is needed to fully understand the mechanisms of LLLT and to optimize its use in mainstream medicine.