Systems, methods, and apparatuses for monitoring end stage renal disease

An end stage renal disease (ESRD) monitoring system may include an implantable sensor and a reader device with an optical sensor. The implantable sensor may be configured to detect a group of analytes relevant to ESRD, such as glucose, creatinine, urea, and potassium. The implantable sensor may be implanted into the dermis of an animal, and may exhibit color changes in response to the presence of the target analytes or reaction product(s) thereof. The reader device may be configured to capture an image of the implanted sensor and to determine the concentration of the target analytes based at least in part on the image. The reader device may be a personal electronic device such as a cell phone, PDA, or personal computer.