Optimising HbA1c monitoring intervals in patients with type 2 diabetes based on glycaemic control status: a target trial emulation study

The recent target trial emulation by Wang et al. provides an important step towards answering a practical question in type 2 diabetes (T2DM): how often should HbA1c be measured? Using electronic health records from 183,078 adults, the authors found that longer monitoring intervals were not associated with worse outcomes among patients with HbA1c <7%, whereas longer intervals were associated with increased mortality and/or cardiovascular risk among patients with higher HbA1c. Their proposed intervals of 1.5–2 years, 6 months, and 3 months for HbA1c <7%, 7–7.9%, and ≥8%, respectively, offer a more explicit framework than broad guideline ranges.¹

This is valuable because evidence for monitoring long-term conditions has historically been limited. Previous work has demonstrated substantial variation in laboratory testing in primary care, while earlier reviews found that many monitoring recommendations relied on expert opinion rather than direct evidence.^2,3 More recently, Elwenspoek et al. found strong evidence for only a limited number of routine T2DM monitoring tests, including HbA1c and eGFR.⁴

However, HbA1c alone may be an incomplete basis for determining monitoring intervals. Two patients with the same HbA1c may have different risks because of treatment intensity, recent medication changes, hypoglycaemia risk, diabetes duration, kidney disease, frailty, comorbidity, or a changing glycaemic trajectory. The study itself allowed temporary intensification of monitoring when clinically important changes occurred, illustrating that intervals cannot be completely static.¹

A useful next step would therefore be to develop and validate multidimensional risk-stratified monitoring strategies rather than relying on HbA1c thresholds alone. These could combine current HbA1c with its trajectory, treatment changes, renal function, hypoglycaemia risk, diabetes duration, and relevant comorbidity. Validation should also extend beyond a single health system to assess generalisability in routine practice.¹

The question may therefore be evolving from “How often should we test HbA1c?” to “Which patient needs which test, at what interval, and what action will the result trigger?” Evidence-based, risk-stratified monitoring could reduce low-value testing while ensuring that patients whose risk is changing are reviewed promptly.

References

1. Wang B, Tse ETY, Li S, Wu H, Chui CSL, Lam CLK, Wan EYF. Optimising HbA1c monitoring intervals in patients with type 2 diabetes based on glycaemic control status: a target trial emulation study. BJGP Open, 2026. doi:10.3399/BJGPO.2025.0020

2. Jones T, Patel R, Elwenspoek MMC, Watson JC, Mann E, Alsop K, Whiting PF. Variation in laboratory testing for patients with long-term conditions: a longitudinal cohort study in UK primary care. BJGP Open, 2023;7(1):BJGPO.2022.0139. doi:10.3399/BJGPO.2022.0139

3. Elwenspoek MMC, Patel R, Watson J, Whiting P. Are guidelines for monitoring chronic disease in primary care evidence based? BMJ, 2019;365:l2319. doi:10.1136/bmj.l2319

4. Elwenspoek MMC, O'Donnell R, Jackson J, Dawson S, Charlwood K, Hay AD, Watson J, Whiting PF. Evidence-based tests to monitor adults with type 2 diabetes mellitus in primary care: rapid reviews and consensus process. Br J Gen Pract, 2025;75(760):e730-e738. doi:10.3399/BJGP.2024.0744