I did a bit of research online, and found the following information, which may be helpful. I would definitely suggest discussing it with your dietitian if you are diabetic. I did find a website that claimed fructose was NOT a good substitute for glucose for diabetics, but it was specifically referring to corn syrup, which I would not recommend anyway. Fructose as naturally occurring in fruit and honey, is what is used in the granulated fructose that I buy.
Here's what I found on a medical site online:
Q: What is the difference between consuming glucose and fructose? Do they both raise blood sugar levels?
A: Either glucose or sucrose will raise blood sugar almost immediately when ingested and are not recommended for people with hypoglycemia or diabetes. However, fructose must be converted to glucose in the body in order for it to actually raise blood sugar levels; this conversion takes some time. So, when fructose is consumed, blood sugar levels do not rise immediately and insulin levels do not rise greatly. Fructose, consumed in moderate levels, appears to be a safe, natural sweetener for those with blood sugar problems. Very high fructose consumption may raise triglyceride levels. This level of consumption would occur if fructose-sweetened products were eaten frequently throughout the day.
Editor's note: high-fructose corn syrup, a super-concentrated (super-sweet) commercial fabrication, is not being recommended here.
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I am sure there are brands you can find if you live in the United States. Here in Australia we have Fruisana, a granulated white fruit sugar that comes in a box for about $3.50. You may want to check out the website for Fruisana, the sugar I use, but I doubt it's available in the States: http://www.fruisana.com