My 20 year old son has always been thin and was diagnosed with type 1 diabetes 18 months ago with a blood glucose of 700 mg/dl [38.9 mmol/L]). Every three months when he goes in for a check-up, we’ve insisted on running tests, his C-peptide is within normal range and he tests negative to antibodies every time. He appears to have good control, yet he has occasional periods of extreme lows, and due to rebound effect, it seems to take him over a week to stabilize. He doesn’t take much insulin (less than the amount I’ve seen suggested for body weight), and his doctor has said he has severe lows because he will spontaneously produce insulin.

For a while his doctor had him on pills, but after a time took him off the pills, and his now on Lantus with Humalog. Since being on insulin he has gained weight, but certainly isn’t overweight. I’m an extremely confused. I have questioned what is going on since my son has no antibodies. Should we be requesting he be treated as someone with type 2 diabetes and have him on pills instead of insulin?

It is sometimes difficult to establish the precise type of diabetes that an individual has. It is precisely for this reason, such as situations like your son, we don’t use the terms of “juvenile onset” and “adult onset” diabetes, but is not always easy.

As for type 1 versus type 2 diabetes in your son, my approach would be the following, depending on answers to some questions. In a thin 20 year old who had a blood glucose of 700 mg/dl [38.9 mmol/L], I would also treat him as someone with type 1 and would provide insulin, almost regardless of how “little” he needed. Did he present with ketosis also? He is probably in the “honeymoon phase” of diabetes, which explains why his doses of insulin had been able to be diminished, but I personally would not try aggressively to get him off insulin. He must check his glucose levels frequently. There is a late-onset, antibody-negative form of type 1 diabetes. Perhaps it is due to anti-pancreatic antibodies that we don’t yet identify. Perhaps, your son’s doctor is not requesting the most sensitive type of antibodies to measure or is sending the blood to a less accurate lab. You might wish to confirm that they have requested GAD-65 and ICA-512 antibodies. Good labs would be Barbara Davis Diabetes Center in Denver, University of Miami, University of Florida in Gainesville, Esoterix Reference labs, and perhaps others that might include Mayo Clinic reference labs or Quest-Nichols lab in California. I don’t think testing every three months for antibodies is cost-effective.

The presence of C-peptide does not confirm that this is type 2 diabetes. However, a special test that your doctor might want to consider is called an intravenous glucose tolerance test in order to measure the “first-phase” insulin response. This is an easy test but requires very good preparation by your son and the lab giving the IV glucose and withdrawing the blood. In essence, the patient has an IV line started (a big enough one so that blood can be withdrawn!!) and a baseline “Time 0” sample of blood is drawn. He then receives a quick IV bolus of glucose (special dose dependent upon body weight) and then blood is immediately withdrawn after 1 minute, 3 minutes, 5 minutes, and 10 minutes. All the blood samples are analyzed for glucose and insulin. The sum of the insulin levels in the 1 and 3 minutes samples are called the “first phase” levels, and normal should be greater than 100 uU/mL. If less, this confirms a state of insulin deficiency, or type 1 diabetes.

DS