My guess is that your husband has late-onset type 1 diabetes, sometimes called LADA (Latent Autoimmune Diabetes of the Adult). Most cases of type 1 diabetes result from the immune system attacking and destroying the insulin producing cells of the body. We call this an “autoimmune” process, and there are many other diseases, such as hypothyroidism, rheumatoid arthritis and multiple sclerosis, that result from such immune damage. We still do not understand precisely what triggers the autoimmune reaction, but in most cases it is thought to be the result of a virus infection of the insulin-producing cells of the pancreas. The thing is, once this problem gets started, it can progress at different rates. If the process starts in one boy at age 8 and progresses quickly, he may develop diabetes by age 10 or 11. If the process starts in another boy at the same age but progresses very slowly, he may not develop diabetes until his 30s, 40s or even later. Even though the two individuals developed diabetes at very different ages, it is still fundamentally the same process.
Often, people with this form of diabetes are misdiagnosed to have type 2 diabetes because of the age at which they develop the condition. And they often respond to oral medications during the first few months or years because they still have some insulin production, which tends confirm the misunderstanding of their condition. But someone with late-onset type 1 diabetes will usually need insulin relatively quickly. The clues to this condition are exactly those that you mentioned-the person does not have any family history and is not overweight.