Like what do they mean by bad days. do they get weak and stuff.

the longer you have it you start to get problems with circulation and suck, possibly they ate too much sugar and spiked they're blood sugar or went to low.. etc. when your blood sugar is not stable around 4-5 it effects your energy levels.

depending on how well they control the glucose levels, they can feel bad, sick woozy, etc if they go low or hypo and have to do the sugar eating thing without proteins to balance it.

They can skip their insulin so they can lose some weight and go high then they feel like cra*!

Either way they do not feel good at all.

Diabetes is very hard to control. It takes a lot of diligence. It is even harder for type 1's. Everything u eat & drink or do not eat or drink affects ur blood sugar. In type 1 is their body no longer makes insulin, so they must be diligent about counting their carbs at every meal, checking their blood sugars & then giving themselves the right amount of insulin. And even with all that work, u r never guaranteed to have it just right, so sometimes ur sugar can go to high or too low. It is a delicate balance & if u go out of ur target range too much in either direction, u will feel sick, tired, grumpy, etc. So sometimes it is just a ''bad day'' Not to mention it is a lot of hard work everyday to be diabetic & u get no break from it, so it could be that they r just having a bad day emotionally & that too will affect ur blood sugar. l hope that helps you!