Sayang, GDM during puasa is really something you MUST discuss with your doctor or diabetes specialist dulu, okay? This isn't something to figure out on your own because it affects both you and baby, they need to check your blood sugar levels and give you the green light (or adjust things) before you start puasa. I know a few mum friends yang ada GDM, and they all worked closely with their gynae to create a safe plan, some managed to puasa with medical support, some didn't, depending on their individual situation. The menggigil and dizziness you're worried about is real and serious, so jangan take chances! Please book an appointment with your doctor soon and be honest about wanting to puasa. They're there to help you, not judge. Take care of yourself and baby first, ya? The ibadah will be there, but your health comes first.