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Why can't people with type 1 diabetes make enough insulin?

People with type 1 diabetes can't make enough insulin because the cells in the body that make insulin have been destroyed. Insulin is a hormone made in the pancreas by beta cells. In people with type 1 diabetes, the immune system mistakes beta cells for bad guys and attacks them, so they can no longer make insulin.

Dr. Jack Merendino, MD
Endocrinologist

The essential definition of type 1 diabetes is that people make little or no insulin, but the answer isn't as simple as that.

Type 1 diabetes most often results from an autoimmune process that leads to the loss of beta cells, the cells in the pancreas that manufacture and release insulin. Someone with fully developed type 1 diabetes will often make little or no insulin. However, the autoimmune process does not lead to a loss of insulin in one step or overnight, and some people lose their insulin production very gradually. These are usually people who are diagnosed with type 1 diabetes relatively late--in their 30s, 40s or later. When they are first diagnosed, they often still make a fair amount of insulin. They are often thought to have type 2 diabetes, and because they still make a good deal of insulin they usually respond to oral medications, reinforcing the idea that they have type 2 diabetes. However, as they continue to lose beta cells, their insulin production declines, and eventually they need insulin treatment to maintain blood sugar control.  It may take several years from the time of their initial diagnosis  to progress to this point.

The other thing to note is that even people with fully-established type 1 diabetes differ in terms of how much insulin they make. Some people still make enough insulin to help smooth out the fluctuations in blood sugar that you typically have with insulin injections or an insulin pump. These are people who are easily controlled and have good hemoglobin A1c levels and very few episodes of hypoglycemia without very much effort. These people often have low but detectable levels of C-peptide, a marker of insulin production by the body. Other people make virtually no insulin. They typically have a much harder time achieving good blood sugar control without having many episodes of low blood sugar.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

In people with type 1 diabetes, the pancreas makes very little or no insulin, which we all need to live. Watch the video to learn more about type 1 diabetes.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.