**Background:** People with diabetes mellitus (DM) have an estimated two- to three-times greater risk of adverse tuberculosis (TB) treatment outcomes compared to those without DM. Blood glucose control is a primary aim of managing DM during TB treatment, yet TB programmes are not generally adapted to provide DM services. The purpose of this study was to understand perceptions and the lived experiences of diabetic patients in TB treatment in the Philippines, with a view to informing the development of disease co-management strategies.
**Methods:** This explanatory, sequential mixed methods study was conducted within the Starting Anti-TB Treatment (St-ATT) prospective cohort of 901 non-pregnant adults (≥18 years) initiating TB treatment for drug-sensitive and drug-resistant TB at 13 public TB-DOTS clinics in three regions of the Philippines (Metro Manila, Cebu, Negros Occidental). From the subset of 189 diabetic persons (self-reported prior DM diagnosis or diagnosed by screenings conducted through the TB clinic), longitudinal glycosylated haemoglobin (HbA1c) data were used to ascertain glycaemic control (controlled or uncontrolled). Univariable logistic regression analyses exploring associations between uncontrolled glycaemia and demographic and clinical factors informed purposive sampling of 31 people to participate in semi-structured interviews. Interviews were conducted in local languages (Tagalog, Cebuano, Hiligaynon, or English) by trained research assistants, lasting 30–60 minutes. Data were analysed using a reflective thematic approach, with coding based on an adapted Theory of Diabetes Self-Care Management and Health Belief Model.
**Key Results:** Among the 189 TB-DM patients, 151 had HbA1c data available; 66 (43.7%) had uncontrolled glycaemia. Significant univariable associations with uncontrolled glycaemia included: region (Manila vs Cebu: OR 10.35, 95% CI 2.17–49.49, p=0.012), BMI classification (overweight/obese vs normal: OR 1.94, 95% CI 0.77–4.90; underweight vs normal: OR 0.39, 95% CI 0.16–0.92, p=0.016), central obesity (OR 3.47, 95% CI 1.62–7.41, p=0.001), timing of DM diagnosis (previously diagnosed vs newly diagnosed: OR 4.69, 95% CI 2.33–9.42, p<0.001), use of metformin (OR 5.31, 95% CI 2.49–11.32, p<0.001), use of insulin (OR 4.31, 95% CI 1.46–12.67, p=0.008), experience of DM complication (OR 2.23, 95% CI 0.91–5.45, p=0.048), and relapse vs new TB case (OR 0.46, 95% CI 0.23–0.93, p=0.029).
Qualitative findings from 31 participants (median age 52 years, range 30–83; 22 male; 12 controlled, 14 uncontrolled, 5 indeterminate) revealed four main domains: (1) Knowledge, attitudes, and beliefs: Participants were generally knowledgeable about DM and its management, but a minority were aware of the impact of DM on TB treatment outcomes. Many preferred phytotherapy (e.g., bitter gourd, okra, malunggay) over glucose-lowering medications due to fear of side effects. (2) Illness perception: Many participants (12/31) relied on body cues rather than blood glucose monitoring to assess glycaemic control. Those with uncontrolled glycaemia more often reported that acute TB illness motivated them to start DM self-care. (3) Self-care agency: TB disease and its treatment (e.g., weight loss, nausea, appetite loss) were barriers to engaging in diabetic self-care activities such as diet restriction and exercise. (4) Access to resources: Free glucose-lowering medications through TB-DOTS were a key enabler, but stock-outs and lack of awareness of available services were barriers. Twelve participants were newly diagnosed with DM through TB screening; only two had perceived any diabetic symptoms prior. Financial incentives (e.g., 250 PHP per follow-up for St-ATT, 700 PHP weekly allowance at PMDT centres) helped some purchase insulin or needles.
**Clinical Implications:** TB-DOTS clinics can serve as a key point of connection to diabetes resources, particularly for patients newly diagnosed through TB screening who might otherwise remain undiagnosed. TB programmes should consider identifying patients with complicated DM (e.g., previously diagnosed, requiring insulin) and offering integrated monitoring and management, as DM and diabetic complications may compound the burden of TB and its treatment. Ensuring continuity of DM care after TB treatment completion, especially for patients on insulin, is critical. Health education should address mistrust of glucose-lowering medications and provide culturally appropriate guidance on phytotherapy use. The Department of Health should strengthen Universal Health Coverage to ensure reliable access to DM services, including blood glucose monitoring and medications.