Hi Brandy, and, of course, your friend's Grandmother's cat (his name would be helpful...),
I'm sorry about your friend's Grandmother. Something tells me her new place as an angel is looking down on you warmly and with love for taking in her sweet furry boy... Bless you, Brandy.
My humble suggestion is to start home testing your friend's Grandmother's older furry gent (see how his name would fit in here?). Although Lantus is a wonderful insulin for a diabetic cat, 11 units BID is pretty much beyond my comprehension in terms of a whopping dose. Unless, of course, he has other medical issues such as Acromalgy (sp?) or Cushing's... Even though he's a big boy, chances are he may not need that aforementioned whopping dose. It's really good you're calling his vet to get the dosing straightened out. Bless you, Brandy.
You can get a human glucometer kit for almost or maybe free, after rebates, from Wal-Mart, Target, CVS, Walgreens, or whatever drug store or mass merchandiser with a pharmacy. The kits usually come with the meter, 10 strips, and 10 lancets. Many here really like the Wal-Mart Reli-On meter (think there's two kinds). Their test strips are less expensive. Believe it or not, you'll need a sock with a small handful of uncooked rice in it that you'll put in the microwave for about 20 seconds, depending on the sock thickness and your microwave wattage. A warm ear is a giving ear... You'll also need Vaseline as it helps bead the very tiny drop of blood you'll be getting from your friend's Grandmother's furry gent's ear (name...).
You can also request a newbie kit from one of the links on the top of the page. It will have what you need for basically the price of postage. Do pick up a meter kit locally to buy you some testing time before your newbie kit arrives, should you request one. Having a couple of meters around never hurts, Brandy.
Okay, let's move on to the food your friend's Grandmother's furry boy (name...) eats. You mentioned Science Diet Hair Ball Control, right? Is this dry food or canned food? We generally recommend a low carb, high protein diet for sugar cats. Something like Fancy Feast Classic or Friskie's pate. I'll give you the link to Janet and Binky's Famous Food Charts. But, before I do, want to humbly explain how much a diet change can affect a diabetic cat's need for insulin. TONS!
Sue's Oliver dropped something like 100 points in his BG (blood glucose) reading after switching from dry food to wet food. Thus, the importance of home testing. Make sense? Had she not been home testing, Sue wouldn't have known and might have given Oliver too much insulin. Too high is do-able for a time. Too low for an instant, can be an incredibly serious situation.
Okay, let's consider your friend's Grandmother's cat (...). He's getting this big whopping dose of insulin. My extremely humble suggestion is to let him eat whatever he wants to eat until you can figure out his dosing with his vet -- and, you start home testing. Then, and only then, I extremely humbly suggest you start transitioning his diet s-lo-w-l-y -- I'm talking adding a teaspoon at a time of the wet food to the dry food. If he seems to like it, add another teaspoon and start removing some of the dry. This process could take a couple of weeks. The most important thing is that he eats. Period.
Here are the links to Janet and Binky's Famous Food Charts:
Dry food:
http://binkyspage.tripod.com/dryfood.html
New wet/canned food:
http://binkyspage.tripod.com/CanFoodNew.html
Old wet/canned:
http://binkyspage.tripod.com/CanFoodOld.html
There's also a link to Dr. Lisa's website at the top of this page. It will explain the raw diet, which is definitely another way to go -- s-l-o-w-l-y.
One more thought. Lantus likes a 12/12 schedule. Meaning, dear Brandy, once you get your friend's Grandmother's furry gent's proper dosing figured out with his vet, you pick the times (morning and evening) where you can test and shoot pretty much 12 hours apart that best suits your schedule. Making this work for you is very important. Bless you, dear Brandy!
Welcome to the place you never wanted to be; but, will be blessed for having found.
Love and encouraging hugs,
Deb and Nikki -- and, Giz, forever dancing in my heart...
PS: Long ago and far away, my dad was a brigade commander at Fort Gordon, GA. Deep in the woods of that massive Fort, he and his troops started an unofficial sanctuary when they found unexpected critters... I was 16 at the time and learned a monkey can actually poop in mid-air swing... Also learned that pythons are surprisingly dry and warm as opposed to cold and wet like I thought...