Introduction and objective:
Loss to follow-up (LTFU) along the TB care cascade is a barrier to TB control because of sustained TB transmission including resistant strains, high mortality and increased spread of DRTB strains. Understanding common reasons for LTFU and their timing could help target interventions to improve adherence to TB treatment.

Material and methods:
A cross-sectional study using pre-tested questionnaires were administered by phone interviews to 90 TB patients receiving treatment between January – December 2020 who were LTFU while on TB treatment in 31 health facilities across three States in South West Nigeria. The focus of the interviews was to determine the reasons why they were LTFU. Interviewers contacted treatment supporters when patients could not be reached. Clinical and socio-demographic information, such as age, sex and HIV status were extracted from treatment registers

Results:
The mean age of patients was 42.6 years (16–90) and SD=17.2. The majority 73 (81%) of LTFU were male, while Ogun State had the highest number – 35 (38.9%), LTFU was highest during the first month on treatment – 60 (66.7%), among HIV negative – 63 (70%), and those who had not been treated previously for TB – 85 (94.4%). The most common reason for LTFU among TB patients on treatment was death – 23(25.6%), followed by lack of transport – 16 (17.8%), and religious beliefs – 12 (13.3%).

Conclusions:
The study suggests a high mortality among patients receiving treatment who may have been classified as LTFU. Interventions to reduce mortality and increase coverage of TB treatment facilities, thus bringing care closer to patients, is necessary. It is suggested that 30-day adherence calendars should be used to improve adherence counselling in the first one month on treatment to minimize early LTFU among TB patients.