BACKGROUND: Worldwide, there has been an increase in type 2 diabetes mellitus (DM2) as a comorbidity of tuberculosis (TB), which is characterized by alterations in the pharmacokinetics of drugs used for TB treatment.OBJECTIVE: To characterize the pharmacokinetics of rifampin in patients with TB and TB-DM2.METHODS: Blood samples were collected in two hospitals in Baja California, Mexico from March through December 2017. Sampling was not random and included 14 patients with TB and 16 with TB-DM2. High-performance liquid chromatographic (HPLC) was carried out to determine the concentration of rifampin in human serum.RESULTS: On average, the highest concentration of rifampin for both groups was registered at 2.5 h after ingestion (3.5 ± 2.64 μg/ml). The maximum difference in concentration (Cmax) of rifampin between TB and TB-DM2 group was not significant (P > 0.05). Importantly however, the analysis showed suboptimal levels of Cmax in a high proportion of both groups of patients studied.CONCLUSION: The study suggests that under the currently recommended rifampin dose, suboptimal Cmax levels are reached in a high proportion of patients, regardless of whether they have diabetes or not. It may therefore be necessary to use higher doses of rifampin and perform routine monitoring of serum levels. However, further work is needed to confirm these findings.