A temperature measuring method of a patient, comprising the following steps: - detecting, by a non invasive infrared thermometer with measurement at a distance and without direct contact, the intensity of an infrared radiation coming from at least one region of interest of a patient, for determining the temperature of said region of interest; said thermometer being of the portable type and comprising a main holding body, defining a grasping region, and means for detecting the infrared radiation; - pointing at least one target area coincident with said region of interest, wherein said step of detecting the intensity of an infrared radiation from a patient's region of interest comprises a sub-step of detecting the infrared radiation coming from one eye, characterised in that the method further comprises the steps of - determining a condition of correct positioning of the means for detecting the infrared radiation to a predetermined distance "D" from the target area through control means operatively associated with the main holding body and cooperating with a processing unit, said control means comprising light emitters or pointing lights providing two or three visible light beams that are non-coplanar with each other and convergent towards the target area, and - displaying the target area by projection of a pointing shape around said target area, the pointing shape having a conformation adapted to circumscribe a predetermined portion of the eye wherein said predetermined portion of the eye is a cornea portion and/or a pupil and/or an iris of the eye, the step of pointing the thermometer to the eye being without directing the light beam constituting the pointing shape towards the pupil. - detecting, by a non invasive infrared thermometer with measurement at a distance and without direct contact, the intensity of an infrared radiation coming from at least one region of interest of a patient, for determining the temperature of said region of interest; said thermometer being of the portable type and comprising a main holding body, defining a grasping region, and means for detecting the infrared radiation; - pointing at least one target area coincident with said region of interest, wherein said step of detecting the intensity of an infrared radiation from a patient's region of interest comprises a sub-step of detecting the infrared radiation coming from one eye, characterised in that the method further comprises the steps of - determining a condition of correct positioning of the means for detecting the infrared radiation to a predetermined distance "D" from the target area through control means operatively associated with the main holding body and cooperating with a processing unit, said control means comprising light emitters or pointing lights providing two or three visible light beams that are non-coplanar with each other and convergent towards the target area, and - displaying the target area by projection of a pointing shape around said target area, the pointing shape having a conformation adapted to circumscribe a predetermined portion of the eye wherein said predetermined portion of the eye is a cornea portion and/or a pupil and/or an iris of the eye,