A method and a mobile app are disclosed for obtaining hemoglobin count in the blood of a mammal using digital images of the conjunctiva of the eye of the mammal taken with a camera of a mobile device running the mobile app. The mobile app carries out a method including: obtaining a color image of the conjunctiva of the eye using the digital camera； computing an R/B ratio and a Y/I ratio of the color image； normalizing the R/B ratio and the Y/I ratio using color image normalization parameters obtained using a master camera so as to provide a R/B true ratio and a Y/I true ratio； and using the R/B true ratio and the Y/I true ratio as inputs to respective look-up tables created using the master camera so as to provide an accurate measure of blood hemoglobin count.
