Those that suffer from type 2 diabetes are told to limit their intake of carbohydrates. This is normally doable. However comes the Seder night, with 4 cups of wine and significant Matza intake one is going to be significantly over the amount of carbs recommended. Does any contemporary Poseik discuss this and have suggestions as to how to limit the carbs?
There's a Jewish Diabetes Association - guide for diabetics that puts out a list of the minimum shiurim; normally we say "oh play it safe and eat a larger amount of matza/wine just to be safe", but for those with medical conditions, we can safely follow the opinions that a much smaller measure is required.
Obviously, if someone just can't do it, they just can't do it.
There are matzas available that have more bran than naturally occurs in whole wheat; the mishna says this is acceptable. I don't know if they're available in shmurah, though. (If the added-bran machine matza is what's medically indicated, and no lower-carb shmurah matza is available, it would not surprise me if a rabbi felt this was the best way to do the mitzva.)
With the wine, please buy small cups. There are plenty of solid rabbinic opinions that 4 fluid ounces or less is all that's needed (and you don't even have to drink the entire cup), but people are used to humongous cups. There is also some room for diluting the wine / grape juice as well.
The linked guide has more details.