What does delaying beta-cell loss really buy you?
The most compelling benefit of preserving beta-cell function is a lower risk of severe hypoglycemia—dangerously low blood sugar that can cause seizures or unconsciousness. In a long-term study of people with type 1 diabetes for an average of 35 years, those with the highest residual C-peptide (a marker of insulin production) had a 27% rate of severe hypoglycemia, compared with 70% in those with no residual function [5]. That's a dramatic difference in safety, even if it doesn't change your daily insulin dose much.
But the effect on day-to-day glucose control is less clear. A 2025 meta-analysis of 19 trials found that immunotherapies preserved C-peptide but did not improve HbA1c (average blood sugar over 3 months) [2]. This suggests that while your own beta cells are working, they help buffer against extreme lows, but the overall glucose control may still depend on how well you manage insulin and diet.
Why do trials show preservation but not better glucose control?
The best-case scenario comes from the PROTECT trial, a large phase 3 study of teplizumab in 217 children and adolescents with newly diagnosed type 1 diabetes. It showed a significant preservation of C-peptide at 78 weeks, with 94.9% of treated patients maintaining a clinically meaningful level compared to 79.2% on placebo [1]. However, there was no significant difference in insulin doses, HbA1c, or time in target glucose range—the outcomes that matter most for daily management [1].
This disconnect likely happens because in trials, everyone receives intensive insulin management, which can mask the benefit of preserved beta-cell function. The meta-analysis noted that the lack of HbA1c improvement might be due to this 'intensive insulin management masking treatment benefits' [2]. So, in real-world practice, preserving beta cells might still help, but the trials don't prove it because they're designed to keep glucose controlled in all participants.
Another example is verapamil, a blood pressure drug that showed a 30% higher C-peptide level at 52 weeks in a randomized trial of 88 children [3]. Yet, the difference in HbA1c was not statistically significant (6.6% vs 6.9%) [3]. So, while your own insulin production is better, it doesn't automatically translate into a lower A1c in the trial setting.
Does the benefit last over the long term?
The evidence suggests that the preservation effect fades over time. The meta-analysis found that the reduction in insulin requirements diminished progressively, with time explaining 49% of the variation in treatment effect [2]. This means that the initial benefit of preserving beta cells may not persist for years without ongoing treatment.
However, even a temporary preservation can have lasting safety benefits. The long-term DCCT/EDIC study showed that people who had any residual C-peptide after 35 years had a lower risk of severe hypoglycemia, and this was associated with higher C-peptide levels at diagnosis [5]. So, early preservation might set the stage for a 'honeymoon' that reduces hypoglycemia risk for decades, even if it doesn't fully stop the disease.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2021 to 2025, 1 from 2024 or later, 4 in Q1 journals, collectively cited 517 times — selected as the most relevant from 7 studies that passed quality screening, drawn from 57 papers retrieved from a database of over 500 million.
Sources used in this answer
Teplizumab and β-Cell Function in Newly Diagnosed Type 1 Diabetes
In a phase 3 randomized trial of 217 children and adolescents with newly diagnosed type 1 diabetes, teplizumab preserved C-peptide at 78 weeks (mean difference 0.13 pmol/mL) but did not improve insulin doses, HbA1c, or time in range.
Immunomodulatory interventions in type 1 diabetes: a systematic review and meta-analysis revealing paradoxical dissociation between beta-cell preservation and glycemic control
A meta-analysis of 19 trials (n=1,852) found that immunotherapies preserved C-peptide (SMD=0.221) but did not improve HbA1c, and insulin reduction benefits faded over time (R²=49%).
Effect of Verapamil on Pancreatic Beta Cell Function in Newly Diagnosed Pediatric Type 1 Diabetes
In a randomized trial of 88 children, verapamil led to a 30% higher C-peptide at 52 weeks (adjusted difference 0.14 pmol/mL) but no significant HbA1c difference (6.6% vs 6.9%).
Teplizumab: A Disease-Modifying Therapy for Type 1 Diabetes That Preserves β-Cell Function
An integrated analysis of 609 patients from five trials showed teplizumab preserved C-peptide at years 1 and 2 (average increase 0.08 and 0.12 nmol/L) and reduced insulin use by 0.08 and 0.10 units/kg/day.
Residual β cell function in long-term type 1 diabetes associates with reduced incidence of hypoglycemia
In a long-term cohort (DCCT/EDIC, n=944), 12.4% had residual C-peptide after 35 years; those with higher levels had significantly lower rates of severe hypoglycemia (27% vs 70%).