We have to be careful not to offset the health benefits of a vegan diet. There is a surprising amount of evidence suggesting that low-normal iron stores are beneficial and may reduce cancer incidence, mortality and perhaps increase longevity. Specifically, as strongest, I would point out the FeAst study and numerous recent Mendelian randomization studies on iron and longevity (e.g. Daghlas and Gill 2021). It is prudent to test ferritin to know whether you are too low or too high.
Vitamin D testing certainly could be useful, even though recent clinical trials testing vitamin D supplements are between somewhat to highly disappointing, but deficiency is presumably not strongly linked to veganism.
We have to be careful not to offset the health benefits of a vegan diet. There is a surprising amount of evidence suggesting that low-normal iron stores are beneficial and may reduce cancer incidence, mortality and perhaps increase longevity. Specifically, as strongest, I would point out the FeAst study and numerous recent Mendelian randomization studies on iron and longevity (e.g. Daghlas and Gill 2021). It is prudent to test ferritin to know whether you are too low or too high.
Vitamin D testing certainly could be useful, even though recent clinical trials testing vitamin D supplements are between somewhat to highly disappointing, but deficiency is presumably not strongly linked to veganism.