Many of us who have diabetes worry whether we have type 1 or type 2 diabetes. But particularly for those of us who take insulin, it may not be worth the stress. And for many of us it certainly can’t be diagnosed definitively.
Determining which of these two main types of diabetes we have isn’t easy even for endocrinologists, much less the primary care physicians who most often try to help us manage our diabetes. For some of us, none of the tests can tell us for sure whether we have one type of diabetes or another.
Simply put, here’s how the two types differ:
When the cells of your body are resistant for several years to the insulin that the beta cells of your pancreas makes, they compensate by making more insulin. Eventually, however, they works so hard that they can’t keep up and begin to die off. That’s when you get type 2 diabetes.
If you have type 1 diabetes, you usually aren’t resistant to the insulin that your beta cells make. Instead, something else, perhaps an infection, kills most of the beta cells so the rest of the cells in your body get little or no insulin that your body makes.
Whether we take insulin or not, doesn’t determine what type of diabetes we have. Everyone who has type 1 diabetes needs to take regular insulin shots. But about one-fourth of all American adults with type 2 diabetes also takes insulin regularly.
Not knowing which type of diabetes you have can certainly be serious when your blood glucose level is high and you aren’t taking insulin. That could mean you have type 1 diabetes, which requires regular insulin shots.
Lots of us believe that the C-peptide test will tell us what type of diabetes we have. Our bodies form C-peptide during the conversion of proinsulin into insulin. While an insulin or C-peptide level below 5 µU/mL suggests type 1, some recent studies show that people with type 1 can have higher levels. Three years ago a study of 182 people with type 1 diabetes using the most sensitive assay showed that even decades after their diagnosis they had some C-peptide levels and functioning beta cells. And just a few days ago a large-scale study of 924 people with type 1 showed that about one-third of them continue to produce insulin as measured by C-peptide even 40 years after their diagnosis.
Antibody tests can sometimes help our doctors tell us if we have type 1 or type 2 diabetes. Several autoimmune antibodies are associated with type 1 diabetes, including GAD-65, islet cell antibodies, insulinoma-associated antigen, and insulin antibodies, according to "Case Study: New-Onset Diabetes: How to Tell the Difference Between Type 1 and Type 2 Diabetes," in Clinical Diabetes. But this case study goes on to cite a study of 125 people who had recently been diagnosed with type 2 diabetes that found 29 percent of them tested positive for at least one of the four antibodies.
Some doctors think that the way to diagnose type 1 diabetes is diabetic ketoacidosis. But a review of the medical charts of 3,666 young people with diabetes showed that only about one-fourth of them had it when they were diagnosed.
Back in the days when we called one of these forms "juvenile diabetes" and the other "adult-onset," we thought how old we were when we got diabetes would answer the question about which type we have. Now, we know that kids are getting more and more type 2 diabetes and mature adults are also getting type 1.
Even weight or body mass index doesn’t help decide the question. Sometimes it helps to diagnose type 1 diabetes when we have to pee a lot or when we are awfully thirsty or when we lose a lot of weight without trying. Since both type 1 and type 2 diabetes have a genetic component, knowing whether members of our family have one type or the other can also help. Since about 95 percent of us who have diabetes have type 2, that can also be a clue. But these differences aren’t definitive.
You and I can’t answer the question on our own, so why sweat it? Even our doctors can’t always tell for sure.
"Some patients cannot be clearly classified as type 1 or type 2 diabetic," according to what is essentially the bible of endocrinology, the "Standards of Medical Care in Diabetes."
"Many diabetic individuals do not easily fit into a single class," says the American Diabetes Association’s statement on "Diagnosis and Classification of Diabetes Mellitus." Both for our doctor and for us, the statement continues, "it is less important to label the particular type of diabetes than it is to…treat it effectively."
Nothing is worth worrying about. But managing our diabetes is worth all the effort that it takes.
David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.