Toby, I agree with Sarah.
15 or 16 is an extremely harmful blood sugar level, and carries a high risk of permanent damage to much of your body. 5 is a normal blood sugar!
If you feel hypoglycemic at 5, it suggests that your blood glucose is abnormally high most of the time. The solution must surely be to normalise your blood glucose which, with the right diet, can be done using much less insulin. Eating and drinking more sugar is not the answer, it's only compounding the problem.
I'm asuming, from your description, that you're type 2? How much insulin do you use, and what do you eat?
All the best,
fergusc