Diseases and infections are two of the most prevalent problems in the world causing over 300 million illnesses and 5 million deaths annually. Parasitic diseases are rarely studied compared to more common diseases such as cancer and Malaria. This makes any detailed research on them that much more relevant. Specifically, determining the connection between the host’s body size, parasite’s weight, and parasite’s fitness is the main focus of this investigation. It will help us understand the nature of interactions and quantify the impact of the parasite on its host. We have developed a method in which we weigh the barnacle’s shell, the barnacle’s soma, and the parasite or egg mass of the barnacle to compare the relative mass of the parasite or eggs of the barnacle with its host. Preliminary data has suggested that barnacles possibly lose biomass after being infected due to the reduced amount of energy being targeted towards the growth of the barnacle and redirected to parasitic reproduction. Infected and uninfected barnacles share very few similarities in regards to size, reproduction, and egg mass. The data also showed that parasites increase their mass ten times the size of its initial mass throughout the stages of infecting a barnacle. In conclusion, there is a relationship between the size of the parasite and the size of its host because larger barnacle somas can support larger parasites. Further research will provide a more detailed explanation of how parasites affect their host and its impact on the host’s energetics.