Guidance on optimal self-monitoring of blood glucose (SMBG) for adults with type 1 diabetes is limited and inconsistent. Key uncertainties include the optimal timing of monitoring, the ideal frequency of checks, and which glycaemic target values should guide self-testing. Existing studies have not clearly connected different SMBG strategies to patient-important clinical outcomes, and evidence from low-resource settings is particularly scarce. Clarifying these issues is important to support informed and equitable diabetes care worldwide.
The review aimed to assess the effects of different timing, frequency, and glycaemic target values for SMBG on clinical outcomes in adults with type 1 diabetes mellitus.
The authors searched CENTRAL, MEDLINE, Science Citation Index Expanded and Emerging Sources Citation Index (Web of Science), ClinicalTrials.gov, and the WHO ICTRP without language restrictions. The last search date across all databases was 7 January 2026. The review included randomized controlled trials and eligible non-randomized comparative studies with at least 24 weeks duration. Cross-over and cluster-randomised trials, modelling studies, studies limited to pregnant individuals, and studies focusing only on self-monitoring in the context of insulin pump use were excluded.
Eligible study designs: randomised controlled trials and non-randomised comparative studies with minimum 24-week follow-up. Population: adults with type 1 diabetes mellitus. Interventions: differing timing, frequency, or glycaemic target values for SMBG. Exclusions: cross-over and cluster-randomised designs, modelling-only studies, pregnancy-only cohorts, and studies of SMBG solely within insulin-pump management.
Critical outcomes specified were glycaemic control measured by haemoglobin A1c and fasting blood glucose; hypoglycaemia (mild/moderate, severe, nocturnal); diabetic ketoacidosis (DKA); microvascular and macrovascular complications; and quality of life. Risk of bias was assessed using the Cochrane RoB 2 tool for randomized trials and ROBINS-I for non-randomized comparative studies. Certainty of evidence was appraised using GRADE.
A meta-analysis was not conducted because outcome measures and reporting varied across studies and only three eligible studies were identified. The authors followed Cochrane guidance for Synthesis Without Meta-analysis (SWiM), presenting structured tables of study characteristics and effect estimates alongside visual displays of individual study results without statistical pooling. They avoided vote counting by statistical significance.
Three studies met inclusion criteria; together they enrolled 16,481 adults with type 1 diabetes. Geographic settings were in Europe and North America. Study designs comprised one randomized controlled trial (n = 123) and two observational comparative studies (n = 1,159 and n = 15,199). Follow-up durations ranged from 9 to 24 months. All three studies evaluated the frequency of SMBG; no eligible study reported interventions that varied the timing of measurements or predefined glycaemic target values for SMBG.
No eligible studies investigated the timing of SMBG (for example, pre-meal versus post-meal schedules or particular times of day). The review therefore identified no evidence to guide timing recommendations.
All three included studies reported on associations between frequency of SMBG and haemoglobin A1c.
The randomized controlled trial (123 participants) reported a mean change in haemoglobin A1c at nine months of −0.43% in the intervention group versus +0.23% in the control group, yielding an approximate mean difference of −0.66% (95% CI −0.94 to −0.38) favoring more structured and frequent monitoring. The certainty of evidence for this effect was judged very low.
One observational comparative study (1,159 participants) reported that adherence to self-monitoring guidance was associated with an adjusted mean haemoglobin A1c difference of −1.00% (95% CI −1.21 to −0.79) compared with non-adherence.
A large observational study (15,199 participants) found a statistically significant trend of lower haemoglobin A1c with increasing monitoring frequency (P < 0.001), with the lowest A1c values observed among those monitoring more than six times per day.
Across these studies, the evidence that more frequent SMBG may lower haemoglobin A1c was judged to be of very low certainty due to concerns about study limitations, imprecision, and inconsistent frequency categorizations between studies.
No included study reported eligible data on hypoglycaemia (mild/moderate, severe, or nocturnal), diabetic ketoacidosis, microvascular or macrovascular complications, or quality of life. Therefore, the review could not determine whether different SMBG timing, frequency, or target values affect these important patient-centered outcomes.
The review found no eligible studies addressing SMBG timing or glycaemic target values. Three studies examined SMBG frequency and its association with haemoglobin A1c; more frequent self-monitoring may be associated with lower A1c, but the evidence is sparse, heterogeneous, and of very low certainty. Limitations included inconsistent frequency categories, methodological weaknesses in included studies, imprecision, and inconsistency.
Current evidence does not support firm recommendations on optimal timing or glycaemic target values for SMBG in adults with type 1 diabetes. While more frequent SMBG may correlate with lower haemoglobin A1c, the very low certainty of the evidence precludes definitive guidance. High-quality randomized trials and robust comparative studies are needed that: 1) test prespecified timing and frequency strategies; 2) evaluate clinically important outcomes beyond A1c (hypoglycaemia, DKA, long-term complications, and quality of life); and 3) include diverse settings, including low-resource contexts. The review highlights an evidence gap that should inform future research priorities.