This work is aims to evaluate the effect of low level laser irradiation administered intravenously on the level of antibiotic in the blood. A medical semiconductor (GaAs) diode laser device emits a pulsed beam of 200 ns pulse width, radiation at 904 nm wavelength, and average power of 1 mW at 1 kHz pulse repetition frequency with an optical package, constructed locally for this purpose. Twenty eight male adult New Zealand white rabbits were used in this study. They were divided into two groups (control treated with the laser radiation), each group was subdivided into two subgroups depending upon the manner of administration of the Ampicilline, the first one was injected with 10 mg/kg B.W of the Ampicilline at the time of irradiation while the other subgroup given the Ampicilline in a shape of gelatine capsules, each one containing 10 mg/kg B.W orally prior to the anaesthesia, each animal underwent a surgical operation carried out on the medial aspect of the left thigh to expose the femoral vein. Blood of the animals of the treated group was irradiated by introducing the fine needle of the canula into the vein for 5 minutes. Samples of blood were collected from the animals of all groups at the times (0.5, 1, 1, 2, 4, 6, 8, 10, 12, 16, 20, 24, 36, 48 and 72 hours) intervals after the injection of the antibiotic and sent for laboratory analysis using HPLC. The results of this study revealed a significant increase in the level of the Ampicilline (ng/ml) in the treated group as compared with the control one. The increase in the level was significant as compared with the pretreatment time.