Understanding C-Peptide in Type 1 Diabetes

When you think of type 1 diabetes, you probably think about insulin, but there’s another important piece of the puzzle that often gets overlooked: C-peptide. While small in size, C-peptide plays a big role in understanding how the body is (or isn’t) producing insulin. At Rainier Clinical Research Center, we’re committed to advancing progress in type 1 diabetes through ongoing research and meaningful involvement in the search for better care and outcomes.

What Is C-Peptide?

C-peptide, short for "connecting peptide," is a byproduct created when the pancreas produces insulin. When your body makes insulin, it starts off as a larger molecule called proinsulin, which splits into insulin and C-peptide in equal amounts. So, if you have C-peptide in your blood, it means your body is producing (or has produced) some of its own insulin. That’s why C-peptide is more than just a number. It’s a window into pancreatic function.

C-Peptide and Type 1 Diabetes

In people with type 1 diabetes, the immune system attacks the insulin-producing beta cells in the pancreas. Over time, this destruction leads to little or no insulin production and a corresponding drop in C-peptide levels. By measuring C-peptide, researchers and physicians can determine how much insulin the body is still making on its own.

• Higher C-peptide levels may indicate some remaining beta-cell function, especially in early or newly diagnosed individuals.

• Lower or undetectable levels are typically seen in individuals who have had type 1 diabetes for a longer period.

Understanding these levels helps doctors personalize care and helps researchers develop new treatments that aim to preserve or restore insulin production.

Why C-Peptide Matters in Research

C-peptide isn’t just a passive indicator. It’s a tool that helps track disease progression, assess treatment effectiveness, and select participants for clinical trials based on how much residual insulin production they have.

Many type 1 diabetes research studies include C-peptide testing to help evaluate whether a potential therapy may preserve or improve beta-cell function. In some cases, new treatments may help slow the progression of the disease by preserving the cells that produce insulin, and C-peptide is how we measure that success.

‍

‍

Research = Hope

Every blood sample, every data point, and every C-peptide test brings us closer to the goal: a future where type 1 diabetes can be managed more effectively or even prevented altogether. By participating in research, volunteers help pave the way for new therapies, greater understanding, and ultimately, better outcomes for everyone impacted by diabetes.

If you or a loved one has type 1 diabetes, you may be eligible to take part in a clinical study at Rainier Clinical Research Center. Explore our current studies and see how research is moving the needle.

‍