Below is a list of common haematological symptoms of vitamin B12 deficiency. It is unlikely that you will experience all of these, most people will experience one or two. However it is not unusual for people to experience a combination of many of them.
Hyper segmented neutrophils (the presence of hypersegmented neutrophils is an important diagnostic feature of megaloblastic anemia) https://www.labce.com/spg1998426_conditions_associated_with_hypersegmented_neutroph.aspx#:~:text=Hypersegmented%20neutrophils%20may%20be%20seen,deficiency%20(including%20pernicious%20anemia
Macrocytosis (enlarged red blood cells)
Weakness and fatigue
full list of
Signs & Symptoms here