How many types of diabetes are there?
This is a question that we get asked regularly.
If we asked this question to the general population twenty years ago, a majority probably wouldn’t have any idea. But today, unfortunately, so many people have diabetes that everyone seems to at least have heard of type 1 and type 2.
And—due to the rising rate of obesity in pregnant women—the public is becoming much more familiar with gestational diabetes.
However, when you get to the details of this complex disease, things get less and less clear cut—not only how many types of diabetes there are, but also how they’re characterized.
For example, type 1 is an autoimmune disease, and people require insulin at diagnosis. Usually the diagnosis is in childhood, adolescence or early adulthood, but not always (people can be diagnosed with type 1 at any age).
Type 2 isn’t autoimmune, and it may take years before a person requires insulin, if at all—and patients are usually older and often overweight, but again this is a generality, particularly as the number of people who are obese grows and gets younger.
Gestational diabetes occurs during pregnancy, and blood glucose returns to normal after delivery, but often it doesn’t.
In addition, researchers have discovered another category of diabetes called latent autoimmune diabetes in adults (LADA). Think of LADA as a slowly progressing version of type 1 with some of the characteristics of type 2. In fact, some people call it type 1.5.
People with LADA have antibodies to the disease like those with type 1 but they don’t need insulin right away. Their blood glucose can be controlled on lifestyle or oral agents for months or sometimes years.
There’s more. Type 1, 2, gestational diabetes and LADA are polygenic—this means that it takes the involvement of many genes to cause the disease. But there are other, much rarer forms of diabetes that are monogenic, meaning a change in only one gene is responsible for the condition. There are two types of conditions in this category: Maturity Onset Diabetes of the Young (MODY) and Neonatal Diabetes Mellitus (NDM).
MODY
Between 1 and 5% of people diagnosed with diabetes are thought to have MODY.
MODY usually presents in childhood or adolescence but because its symptoms are often mild, many are not diagnosed until much later. Unlike those with type 2, people with MODY are usually of normal weight and don’t have high blood pressure or high cholesterol levels.
Physicians may start to consider a diagnosis of MODY and do genetic testing if there is a history of diabetes in successive generations in the family—grandparent, parent and child. Most often people with MODY can be treated with lifestyle or oral agents.
NDM
Type 1 diabetes is diagnosed after 6 months of age. But there is a rare condition called neonatal diabetes mellitus that can occur from birth to 6 months. Unlike other forms of diabetes, about half of the cases of NDM are temporary. This type of diabetes will disappear in infancy, although it may come back in adulthood. The other half of the cases will continue to have diabetes throughout their lives.