The aim of this study was to evaluate the relationship between HbA1c level and short-term healing of periapical lesions after non-surgical root canal treatment (NSRCT). After NSRCT, digital periapical radiographs were taken and blood samples were drawn for HbA1c analysis. To assess short-term healing (PAI difference), subjects returned after six months for a radiograph and blood draw. A calibration exercise established the reliability of the PAI scoring process. Thirty-eight subjects returned for the recall. The relationship between HbA1c level and also the co-variables, with healing was explained using Spearman’s rho and logistic regression. There was a significant correlation between healing and HbA1c level (rs = -.52, p ≤.0001), age (rs = -.44, p ≤.003), recall days (rs =.29, p ≤.036), and cardiovascular status (rs = -.34, p ≤.018). A final logistic regression showed a significant relationship between HbA1c level and short-term healing of periapical lesions (R = .62, p≤ .05).