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/l ratio of the color image; normalizing the R/B ratio and the Y/l ratio using color image normalization parameters obtained using a master camera so as to provide a R/B true ratio and a Y/l true ratio; and using the R/B true ratio and the Y/l 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.
