Hypoglycaemia linked to QTc prolongation in type 1 and type 2 diabetes: meta-analysis

The study

This is a systematic review and meta-analysis published in Diabetes, Obesity & Metabolism. The authors searched PubMed and the Cochrane Library from January 1990 to January 2026, limited to English-language papers. They included 32 studies in people with type 1 or type 2 diabetes.

The aim was to measure changes in the heart rate-corrected QT interval (QTc) and in sympathoadrenal responses during induced and spontaneous hypoglycaemia. Random-effects models compared hypoglycaemic and euglycaemic states by setting. Subgroup and sensitivity analyses looked at diabetes type, QT correction method and analytical assumptions.

What they found

QTc was prolonged by 44.0 ms (95% CI: 24.3-63.6) under induced hypoglycaemia. Under spontaneous hypoglycaemia it was prolonged by 16.4 ms (6.7-26.0).

By diabetes type, QTc was prolonged by 27.2 ms (12.9-41.5) in type 1 diabetes and 27.0 ms (12.3-41.7) in type 2 diabetes. The all-study summary was a prolongation of 30.2 ms (17.9-42.4).

Other changes were all significant. Heart rate rose by 5.0 bpm and systolic blood pressure rose by 3.1 mmHg. Epinephrine rose by 1.75 nmol/L and norepinephrine rose by 0.66 nmol/L. Diastolic blood pressure fell by 4.4 mmHg and serum potassium fell by 0.44 mmol/L.

Across studies, only the change in epinephrine correlated with the change in QTc after correction for multiple testing (ρ = 0.87). Mean QTc during hypoglycaemia exceeded 450 ms in six studies.

How much weight to give it

The authors describe an association. They state that the direction was robust to all sensitivity analyses but that the size varied substantially between studies. The numbers fit this. Heterogeneity was very high (I2 = 98.4%). The 95% prediction interval for the all-study summary ran from -40.9 to 101.3 ms, so the result in an individual setting could be well away from the pooled figure of 30.2 ms. That figure should be read with caution.

QTc is a surrogate outcome. The abstract does not report arrhythmias, sudden cardiac death or other hard outcomes. It also does not report the number of participants, how the individual studies were designed, risk of bias or funding.

The link between epinephrine and QTc is a comparison across studies. It does not show that epinephrine causes QTc prolongation in an individual patient. Serum potassium also fell, and the abstract does not separate the effects of the different changes. The abstract does not report a formal test comparing type 1 with type 2 diabetes, so the near-identical estimates should not be read as proof of no difference.

For your clinic

The authors conclude that hypoglycaemia was associated with QTc prolongation during spontaneous episodes and under clamp conditions, in both diabetes types. They add that hypoglycaemia avoidance remains a safety consideration in patients with pre-existing repolarisation vulnerability or concomitant QT-prolonging medication.

The abstract reports no clinical outcomes, so it cannot tell you how often these QTc changes lead to harm. Read the full paper before using these data in practice, in particular the study designs, the QT correction methods and the populations included.