Question from Quality, Kentucky, USA:

After seven months, I still do not know what type of diabetes my son has. At diagnosis, his blood sugar was 419 mg/dl [23.3 mmol/L]. His A1c was 7.9. His C-peptide was 3.8 with sugar at 355 mg/dl [19.7]. His insulin production was 21. His endocrinologist said that he had just become diabetic. He did not have acanthosis nigricans. He did not have ketones in his urine. He had lost over five pounds in one month. He has no ancestors with diabetes for at least four generations. He was 16 years old at diagnosis, 5 foot 11 inches tall and weighed 170 pounds. He is now 6 feet tall and weighs 145 pounds, all skin and bones. He is a runner. He has run 12 to 20 miles a week for the last six years.

He controls his diabetes through diet. If he eats under 80 grams of carbohydrates at a meal, then his sugar will stay under 140 mg/dl [7.8 mmol/L]. If he eats 120 grams of carbohydrates at a meal, then he will have sugar readings of 200 mg/dl [11.1 mmol/L]. His early morning readings are always lower than 110 mg/dl [6.1 mmol/L]. His endocrinologist says that she is not ruling anything out, but she is leaning toward type 1B or type 2. She says the laboratory results make her lean toward type 2, but his body style, weight, and history make her unsure. More test are scheduled for July. He is very sensitive to insulin. Seven units of Lantus and three units of NovoLog after a meal of 120 grams of carbohydrates drove his sugar level from 355 mg/dl [19.7 mmol/L] to less than 20 mg/dl [1.1 mmol/L]. Can a diabetic have insulin resistance and be insulin sensitive at the same time? Why would a teenage cross country runner with no family history of diabetes get type 2?