Tattooing is aubiquitous body modification involving the injection of ink and/or dye pigments into the dermis. Biosensors in the form of tattoos can be used to monitor metabolites in interstitial fluid. Here,m inimally invasive, injectable dermal biosensors were developed for measuring pH, glucose,a nd albumin concentrations.T he dermal pH sensor was based on methyl red, bromothymol blue,a nd phenolphthalein, which responded to ap Hr ange from 5.0 to 9.0. The dermal glucose sensor consisted of glucose oxidase, 3,3',5,5'-tetramethylbenzidine,a nd peroxidase that detected concentrations up to 50.0 mmol L À1 .T he dermal albumin sensor consisted of 3',3'',5',5''-tetrachlorophenol-3,4,5,6-tetrabromosulfophthalein to measure concentrations up to 5.0 gL À1 .T he sensors were multiplexed in ex vivo skin tissue and quantitative readouts were obtained using as martphone camera. These sensors can be used to manage of acid-base homeostasis,diabetes,and liver failure in point-of-care settings.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.