BACKGROUND: People with tuberculosis (TB) and their households usually incur large costs for care seeking, diagnosis, and treatment. Diabetes increases the risk of developing TB and has adverse effects on TB outcomes, especially if diabetes is not properly managed. Despite increasing awareness of the importance of managing diabetes within TB programmes, the economic burden of TB and diabetes from the household perspective, costs of diabetes services within the TB programme from the provider perspective, and the cost-effectiveness of providing diabetes services for people newly diagnosed with TB are still unclear. OBJECTIVES: The aim of this PhD was to estimate the societal costs of concurrent TB and diabetes in TB-affected households in the Philippines and evaluate the cost-effectiveness of integrated diabetes screening and management for TB, and in so doing identify the limitations and potential implications of the WHO recommended approach for estimating household costs of TB using a cross-sectional data collection design by comparing it to a longitudinal design. METHODS: Costs and coping mechanisms associated with TB and diabetes from the patient perspective were collected retrospectively from 530 people diagnosed with TB in the Philippines at four timepoints during TB diagnosis and treatment: at TB diagnosis, the end of the intensive treatment phase, and midway and end of the continuation treatment phase (longitudinal design). The results of costs incurred for TB services with the longitudinal design were compared with those with the simulated cross-sectional designs to identify methodological issues in the WHO recommended cross-sectional design of national surveys costs incurred by people with TB and their households. The incremental costs of diabetes screening and management of people with TB from the provider perspective were estimated through a micro-costing of equipment, consumables, and staff time. A simple decision tree model, which includes diabetes screening and management during TB diagnosis and treatment, was developed to assess the cost-effectiveness of integrating TB and diabetes services. All primary TB and diabetes provider costs data, as well as secondary TB provider costs data from a separate TB costing study (VALUE-TB), were incorporated in the model. RESULTS: Using the longitudinal design, the catastrophic cost estimate for TB-affected households was 69%. The catastrophic cost estimates using the simulated cross-sectional design ranged from 40-55%, due to its inherit methodological issues when capturing the reduction and recovery in household income during the episode of TB care. There was no significant difference in the proportion of TB-affected households facing catastrophic costs between those with TB-diabetes (76%) and those with TB-only (69%, p=0.691). From the provider perspective, the cost per a case of people with diabetes detected using different diagnostic algorithms varied from USD 17.43 to USD 80.81. The monthly cost of diabetes treatment per person with diabetes was estimated at USD 8.95 to USD 12.36. Providing diabetes diagnosis and management for people diagnosed with and receiving care for TB would be cost saving: USD 147 per person from a provider perspective and: USD 187 per DALY averted per person from a societal perspective. in the target population of people aged ≥18 years. The probability of the intervention being cost effective was 99% from both the provider and the societal perspectives in people aged ≥18 years, at a threshold of 7.3% of GDP per capita which corresponds to the country specific willingness to pay threshold. The probability of the intervention being cost effective was highest when the intervention was provided in people with BMI >18.5 kg/m2 and those aged >45 years. Hence, I concluded that the intervention would be cost saving from both the provider and societal perspectives and providing the intervention to people with BMI >18.5kg/m2 or those aged >45 years could be an entry point to implement such a policy