I take Topamax, but not for migraines. I take it off label for peripheral neuropathy due to my rheumatoid arthritis. I was originally on Lyrica, but it caused a lot of swelling and water retention. I really like the Topamax, and I haven't had a migraine since I started it. In the past, all my migraines have been blood pressure related (hypertension).
I have noticed that my BGs have increased a little. Originally I was taking it twice a day, and then only once a day in the morning and my BGs were elevated during the day. Now my rheumy has me taking it at bedtime, and my BGs are elevated somewhat when I wake up in the morning. I would say by 10%.
But I would have to say that the Topamax is so much better than Lyrica. No more pins and needles, burning sensations, or numbness in my hands and feet.