In Sigtuna, Sweden, several medieval cemeteries have been excavated, from which approximately 800 skeletons have been excavated and analysed. Archaeological finds and anthropological analyses have exposed social differences between the cemeteries. Stable isotope analyses have shown that the inhabitants of the town consumed a mixed diet. Significant differences in dietary patterns between the cemeteries may be related to social stratification. In the outskirts of a churchyard excavated in 2006, bone changes showing systemic inflammatory disease indicative of leprosy were observed in six individuals. The burial location suggests that the affected belonged to a lower social stratum. Bone samples were taken from these six individuals, 19 other human skeletons and five animals from the same cemetery for analysis of the stable isotope composition of carbon (C), nitrogen (N) and sulphur (S). The results showed no significant differences in δ¹³C and δ¹⁵N values between the groups, i.e. the seemingly healthy humans and the humans affected by severe inflammatory disease appear to have had similar diets. Nor was a significant difference observed in δ³⁴S data between the six affected individuals and the rest of the sample, implying that no difference in origins could be observed between the two groups studied. However, a comparison between the present study and the previous analysis resulted in significant differences in carbon values. Based on the results obtained in this investigation it is suggested that if a dietary difference existed between people in the outskirts of a cemetery (for example those suffering from leprosy) and people buried in higher ranked regions, it was not a difference in food source but rather in other parameters. Instead dietary differences and possibly social variations are demonstrated between cemeteries. The results from the present study highlight the hierarchical arrangements of social classes in the early medieval society.