I take vitamins. I don't eat fully carnivore. We eat meat, poultry, fish, seafood, cheese, eggs, butter. We do eat veg and salad, but will be largely phasing those out for a while, we'll still eat onion, garlic, herbs & spices. Maybe we will sometimes eat a small amount of veg but the majority of our diet will be carnivore. We aren't fanatical about it. It's about eating to get rid of inflammation, for us, and to keep blood glucose lower and stable.
I don't get constipated. I might go to the toilet less, but that's because I eat less filler foods and food that turns into or produces waste from my body. Pretty much most of what I eat, is used, so there's less waste.
As a pp said, part of the way we eat is to try to only eat whole foods, homemade and that give us energy rather than insulin resistance. Wheat, corn, grains all dont really agree with us. My dh can eat some, but I need to swerve them completely.
I need to go quite carnivore for a while to get my bg back under control. I've not been eating correctly and it's higher than it should be.