I have addressed a similar question previously, at http://www.healthcentral.com/diabetes/c/110/21053/companys-denial/

To rephrase my earlier answer:

Arguing with an insurance company is always a multistep procedure.

First, has your diabetes specialist written on your behalf? Do you have copies of the correspondence? The letter must say that the medication is "medically necessary", and should document blood glucose levels, and what other medications have been tried (and failed).

Second, don't assume that the letter was received, if mailed or faxed to the insurance company. Send the letter again, this time by certified mail, with a return receipt requested.

And a copy should go to the Medical Director of the insurance company, not just to the routine address.

Also, send a copy to your employer, if your employment is funding your insurance. And talk to the Human Resources department at the company about what might be done from the employer to help.

Next, plan on rejection (which it seems is already occurring). Write again, and next time, make it clear that a copy is going to your employer (if employed) or to your Congressmen (if government-sponsored insurance).

And finally, document everything!

I have said, only partially in jest, that the first time you write, they throw the letter away. The second time they read it then throw it away. The third time they read it and write back. And the fourth or fifth time, you may eventually find a sympathetic soul who will allow the expense.

Keep on trying!