The low-level laser therapy was used in various biomedical applications for a long time such as improving the rheological properties of blood, wound healing, vascular restenosis, tissue repair. however, its safety has not been well investigated. The present in-vitro study aims to illustrate the influence of low power laser irradiation on the secondary structure of human Haemoglobin (Hb). Fifteen samples of healthy fresh blood have been divided into five groups (3 samples/group) and irradiated using low power infrared laser (wavelength 808 nm, power 4 mw and power density 0.64 mW/cm2) at different irradiation durations (5, 10, 20, 30 min) and zero time for control samples. We used FTIR Spectroscopy followed by some mathematical techniques such as band-narrowing (second-derivative method), spectral subtraction, curve fitting, and integration processes to quantitatively calculate the different contribution ratios of the secondary structure components of irradiated and non-irradiated human hemoglobin samples. It was found no significant change in the contents of the α-helix structure at (5,10,20 min) groups. However, the thirty minutes group (30min) show a significant reduction in the content of α -helix accompanied by a significant increase in the random coil and β-turn structures with (p < 0.05). The decreasing of the alpha-helix structure is explained in terms of photo-inductive degradation to the unordered structure of random coils and β-turns. Extra care has to be taken while the clinical application that includes the intravenous laser irradiation of blood to avoid the protein photodamage caused by the low power laser at long expoture time.