This study systematically evaluates the effects of probiotic interventions on gut microbiota and clinical outcomes in diabetic patients to determine the optimal target population and conditions for effective use, with an emphasis on precision treatment. A comprehensive search was performed across PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Internet (CNKI), and Wanfang databases until April 2024. Randomized controlled trials (RCTs) assessing probiotics as adjunctive therapy for diabetes were included. The control group received standard care, and the intervention group received probiotics alongside standard care. Data were managed with Endnote and Excel, and analyses were conducted using Revman 5.3 and Stata 16. Twelve RCTs involving 1,113 participants were included. Probiotics significantly increased fecal Lactobacillus (standardized mean difference (SMD) 1.42, P < 0.0001, I2 = 95%) and Bifidobacterium levels (SMD 1.27, P < 0.0001, I² = 90%) and reduced fasting plasma glucose (SMD -0.35, P = 0.004). Subgroup analysis showed that shorter intervention durations (≤3 months) improved FPG, HbA1c, and Bifidobacterium levels, while younger patients (≤60 years) experienced the most significant improvements in Bifidobacterium levels. In conclusion, probiotics improve gut microbiota and clinical outcomes in diabetic patients, with intervention duration and patient age as key factors influencing treatment effectiveness.