Timing, Frequency, and Glycaemic Target Values for Self-Monitoring in Adults with Type 1 Diabetes Mellitus.

RATIONALE:Evidence guiding how often adults with type 1 diabetes mellitus should self-monitor blood glucose, when to monitor, and which glycaemic targets to use is limited and inconsistent. The available research has not clearly linked different self-monitoring strategies to meaningful clinical outcomes, and evidence is particularly scarce for low-resource settings. Clarifying these uncertainties is important to support informed decision-making and equitable diabetes care worldwide. OBJECTIVES:To assess the effects of different timing, frequency, and glycaemic target values for self-monitoring of blood glucose (SMBG) in adults with type 1 diabetes mellitus. SEARCH METHODS:We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Science Citation Index Expanded and Emerging Sources Citation Index (Web of Science), ClinicalTrials.gov, and the WHO ICTRP, without language restrictions. The date of the last search across all databases was 7 January 2026. ELIGIBILITY CRITERIA:We included randomised controlled trials and eligible non-randomised comparative studies with a minimum duration of 24 weeks that evaluated different timing, frequency, or glycaemic target values for SMBG in adults with type 1 diabetes mellitus. We excluded cross-over and cluster-randomised trials, modelling studies, studies of pregnant individuals, and studies focused solely on self-monitoring in the context of insulin pump use. OUTCOMES:Our critical outcomes were glycaemic control (haemoglobin A1c and fasting blood glucose), hypoglycaemia (mild or moderate, severe, and nocturnal), diabetic ketoacidosis, microvascular and macrovascular complications, and quality of life. RISK OF BIAS:We assessed the risk of bias in included studies using the Cochrane RoB 2 tool for randomised controlled trials and the ROBINS-I tool for non-randomised comparative studies. SYNTHESIS METHODS:We did not conduct a meta-analysis, as effect measures and outcome reporting varied across the included studies and only three studies met the eligibility criteria. Instead, we followed Cochrane guidance on Synthesis Without Meta-analysis (SWiM) and summarised findings through structured tabulation of study characteristics and results, complemented by visual presentation of individual study effect estimates without statistical pooling. We did not use vote counting based on statistical significance. We assessed the certainty of the evidence using GRADE. INCLUDED STUDIES:We included three studies conducted in Europe and North America, involving a total of 16,481 adults with type 1 diabetes mellitus. One study was a randomised controlled trial, and two studies were observational comparative studies. All studies evaluated the frequency of SMBG; none reported eligible data on timing or glycaemic target values. Follow-up durations ranged from 9 to 24 months. SYNTHESIS OF RESULTS:Timing of SMBG No eligible studies investigating the timing of SMBG were identified. Frequency of SMBG Three studies involving a total of 16,481 adults investigated the frequency of SMBG in adults with type 1 diabetes mellitus. Overall, more frequent self-monitoring may be associated with lower haemoglobin A1c levels, although the evidence is very uncertain. In the randomised controlled trial (123 participants), the mean change in haemoglobin A1c at nine months was -0.43% in the intervention group compared with +0.23% in the control group, corresponding to approximately 0.7% lower haemoglobin A1c with more structured and frequent monitoring (mean difference (MD) -0.66, 95% confidence interval (CI) -0.94 to -0.38). The certainty of the evidence for this outcome was very low. In one observational study (1159 participants), adherence to self-monitoring guidelines may be associated with a 1.0% lower adjusted mean haemoglobin A1c (MD -1.00, 95% CI -1.21 to -0.79) compared with non-adherence. The third study (15,199 participants) reported lower haemoglobin A1c values with increasing monitoring frequency (P < 0.001), with the lowest values among those monitoring more than six times per day. Across both studies, the certainty of the evidence was very low. No included study reported effects on hypoglycaemia, diabetic ketoacidosis, microvascular or macrovascular complications, or quality of life. Glycaemic target values for SMBG No eligible studies investigating glycaemic target values for SMBG were identified. AUTHORS' CONCLUSIONS:No studies evaluated different timings of self-monitoring or different glycaemic target values. Three studies (one randomised controlled trial and two observational studies) assessed the frequency of self-monitoring and haemoglobin A1c. More frequent self-monitoring may be associated with lower haemoglobin A1c, although the evidence is sparse, frequency categories were inconsistent across studies, and the included studies had methodological limitations. The certainty of the evidence was very low for all outcomes, driven by risk of bias, imprecision, and inconsistency across studies. No studies reported hypoglycaemia, diabetic ketoacidosis, quality of life, or other critical outcomes. The evidence is insufficient to draw any firm conclusions about the effects of different self-monitoring strategies in adults with type 1 diabetes mellitus. FUNDING:This review was funded by the World Health Organization through an Agreement for Performance of Work (APW 203512799). REGISTRATION:The review was registered in PROSPERO (CRD42025639736) in February 2025.