That question really should not be only for vegans/vegetarians. There could be a lot wrong with omnivor and other diets as well.
I go and test my blood regularly. It is easy and I feel more data is always a good thing. We are mortal beings and things will go wrong with you. Tracking things is a good way to stay on top of that.
I have hopes in the ongoing trials by Dean Ornish regarding Alzheimer's. It seems all other common age related health issues are improved by a vegan diet, so it will be interesting to see the results of this study.