Although low blood sugar is often associated with diabetes... it can happen in children who are NOT diabetic at all. This is especially the case if a child fasts for too long between meals... or is sick and vomiting. (in fact vomiting a lot can really screw up blood sugar levels even in healthy people)
I would sometimes have low blood sugar as a child if I forgot to eat breakfast and went out to do an activity- it usually caused me to faint. The doctor diagnosed it as "hypoglycemia" and I was just told to eat a piece of hard candy or drink some juice... but ideally, I had to remember to eat!
I was VERY skinny, by the way. So I didn't have much for "fat stores" when I was out playing, which made me more prone to it. When you child gets closer to puberty and towards he shouldn't have as many problems with it... hypoglycemia (literally "low glucose") without diabetes is really uncommon in adults.
However, I did have gestational diabetes with my first pregnancy, but not with my second (because I lost weight and changed my diet)- that means that I do have a higher risk for diabetes down the road if I don't "take care" of myself. I never got type 2 diabetes... phew! Hypoglycemia does not mean you WILL have diabetes... but it is a risk factor and a good reason to make sure your son eats healthfully and doesn't LIVE off of carbs and starches.
So relax... don't "forget" about it- but you don't need to freak out either. 65 is low, but is not REALLY low... next time your son is sick- double your efforts to keep him hydrated, and try to give him pedialyte or some other electrolyte drink if he cannot keep down any foods. If this problem happens again when he is not sick- you could check with the doctor and have him tested for diabetes if you want- but I am pretty sure he is just fine!
Good Luck!
-M.
PS- diabetes itself is actually the opposite of "hypoglycemia"- it is "hyperglycemia"- HIGH blood sugar- BUT, if you have chronic hypoglycemia... that is a risk factor for diabetes- later on in life (to clear that up)