I have been a vegetarian for 49 years and a vegan for the past 32 years of those. I have no problem and the vegan diet is recommended to help control blood sugars, if you eat right! I’m doing well as a type 1 diabetic.
I have found that if I notice I am getting tired more easily, I start drinking a green drink. No not the fruit juice with some greens in it but a drink that is veggie based and has wheat grass, barley grass, chlorella in it. That usually starts to make me feel better right away. It’s something I’ve recommended over the years to people and it almost always seems to help!!! It’s loaded with lots of energy nutrients.
You usually can find a good powder mix at a health foods store. (plus a multiple B vitamin can help with energy levels)